Deployment diagram shows elements as internal although they are external

[MTomBosch]

When defining a deployment view for an external system that contains containers (mainframe in below example) then the elements are shown in blue in the diagram like internal elements although the system in scope is external.

Take this example with the external mainframe system.

/*

• This is a combined version of the following workspaces:
• • "Big Bank plc - System Landscape" (https://structurizr.com/share/28201/)
• • "Big Bank plc - Internet Banking System" (https://structurizr.com/share/36141/) */ workspace "Big Bank plc" "This is an example workspace to illustrate the key features of Structurizr, via the DSL, based around a fictional online banking system." {

  model { customer = person "Personal Banking Customer" "A customer of the bank, with personal bank accounts." "Customer"

  enterprise "Big Bank plc" {
      supportStaff = person "Customer Service Staff" "Customer service staff within the bank." "Bank Staff"
      backoffice = person "Back Office Staff" "Administration and support staff within the bank." "Bank Staff"
  
      mainframe = softwaresystem "Mainframe Banking System" "Stores all of the core banking information about customers, accounts, transactions, etc." "Existing System" {
          mainframeCont1 = container "mainframeCont1"
          mainframeCont2 = container "mainframeCont2"
      }
      email = softwaresystem "E-mail System" "The internal Microsoft Exchange e-mail system." "Existing System"
      atm = softwaresystem "ATM" "Allows customers to withdraw cash." "Existing System"
  
      internetBankingSystem = softwaresystem "Internet Banking System" "Allows customers to view information about their bank accounts, and make payments." {
          singlePageApplication = container "Single-Page Application" "Provides all of the Internet banking functionality to customers via their web browser." "JavaScript and Angular" "Web Browser"
          mobileApp = container "Mobile App" "Provides a limited subset of the Internet banking functionality to customers via their mobile device." "Xamarin" "Mobile App"
          webApplication = container "Web Application" "Delivers the static content and the Internet banking single page application." "Java and Spring MVC"
          apiApplication = container "API Application" "Provides Internet banking functionality via a JSON/HTTPS API." "Java and Spring MVC" {
              signinController = component "Sign In Controller" "Allows users to sign in to the Internet Banking System." "Spring MVC Rest Controller"
              accountsSummaryController = component "Accounts Summary Controller" "Provides customers with a summary of their bank accounts." "Spring MVC Rest Controller"
              resetPasswordController = component "Reset Password Controller" "Allows users to reset their passwords with a single use URL." "Spring MVC Rest Controller"
              securityComponent = component "Security Component" "Provides functionality related to signing in, changing passwords, etc." "Spring Bean"
              mainframeBankingSystemFacade = component "Mainframe Banking System Facade" "A facade onto the mainframe banking system." "Spring Bean"
              emailComponent = component "E-mail Component" "Sends e-mails to users." "Spring Bean"
          }
          database = container "Database" "Stores user registration information, hashed authentication credentials, access logs, etc." "Oracle Database Schema" "Database"
      }
  }
  
  # relationships between people and software systems
  customer -> internetBankingSystem "Views account balances, and makes payments using"
  internetBankingSystem -> mainframe "Gets account information from, and makes payments using"
  internetBankingSystem -> email "Sends e-mail using"
  email -> customer "Sends e-mails to"
  customer -> supportStaff "Asks questions to" "Telephone"
  supportStaff -> mainframe "Uses"
  customer -> atm "Withdraws cash using"
  atm -> mainframe "Uses"
  backoffice -> mainframe "Uses"
  
  # relationships to/from containers
  customer -> webApplication "Visits bigbank.com/ib using" "HTTPS"
  customer -> singlePageApplication "Views account balances, and makes payments using"
  customer -> mobileApp "Views account balances, and makes payments using"
  webApplication -> singlePageApplication "Delivers to the customer's web browser"
  
  # relationships to/from components
  singlePageApplication -> signinController "Makes API calls to" "JSON/HTTPS"
  singlePageApplication -> accountsSummaryController "Makes API calls to" "JSON/HTTPS"
  singlePageApplication -> resetPasswordController "Makes API calls to" "JSON/HTTPS"
  mobileApp -> signinController "Makes API calls to" "JSON/HTTPS"
  mobileApp -> accountsSummaryController "Makes API calls to" "JSON/HTTPS"
  mobileApp -> resetPasswordController "Makes API calls to" "JSON/HTTPS"
  signinController -> securityComponent "Uses"
  accountsSummaryController -> mainframeBankingSystemFacade "Uses"
  resetPasswordController -> securityComponent "Uses"
  resetPasswordController -> emailComponent "Uses"
  securityComponent -> database "Reads from and writes to" "JDBC"
  mainframeBankingSystemFacade -> mainframe "Makes API calls to" "XML/HTTPS"
  emailComponent -> email "Sends e-mail using"
  
  deploymentEnvironment "Development" {
      deploymentNode "Developer Laptop" "" "Microsoft Windows 10 or Apple macOS" {
          deploymentNode "Web Browser" "" "Chrome, Firefox, Safari, or Edge" {
              developerSinglePageApplicationInstance = containerInstance singlePageApplication
          }
          deploymentNode "Docker Container - Web Server" "" "Docker" {
              deploymentNode "Apache Tomcat" "" "Apache Tomcat 8.x" {
                  developerWebApplicationInstance = containerInstance webApplication
                  developerApiApplicationInstance = containerInstance apiApplication
              }
          }
          deploymentNode "Docker Container - Database Server" "" "Docker" {
              deploymentNode "Database Server" "" "Oracle 12c" {
                  developerDatabaseInstance = containerInstance database
              }
          }
      }
      deploymentNode "Big Bank plc" "" "Big Bank plc data center" "" {
          deploymentNode "bigbank-dev001" "" "" "" {
              containerInstance mainframeCont1
              containerInstance mainframeCont2
          }
      }
  
  }
  
  deploymentEnvironment "Live" {
      deploymentNode "Customer's mobile device" "" "Apple iOS or Android" {
          liveMobileAppInstance = containerInstance mobileApp
      }
      deploymentNode "Customer's computer" "" "Microsoft Windows or Apple macOS" {
          deploymentNode "Web Browser" "" "Chrome, Firefox, Safari, or Edge" {
              liveSinglePageApplicationInstance = containerInstance singlePageApplication
          }
      }
  
      deploymentNode "Big Bank plc" "" "Big Bank plc data center" {
          deploymentNode "bigbank-web***" "" "Ubuntu 16.04 LTS" "" 4 {
              deploymentNode "Apache Tomcat" "" "Apache Tomcat 8.x" {
                  liveWebApplicationInstance = containerInstance webApplication
              }
          }
          deploymentNode "bigbank-api***" "" "Ubuntu 16.04 LTS" "" 8 {
              deploymentNode "Apache Tomcat" "" "Apache Tomcat 8.x" {
                  liveApiApplicationInstance = containerInstance apiApplication
              }
          }
  
          deploymentNode "bigbank-db01" "" "Ubuntu 16.04 LTS" {
              primaryDatabaseServer = deploymentNode "Oracle - Primary" "" "Oracle 12c" {
                  livePrimaryDatabaseInstance = containerInstance database
              }
          }
          deploymentNode "bigbank-db02" "" "Ubuntu 16.04 LTS" "Failover" {
              secondaryDatabaseServer = deploymentNode "Oracle - Secondary" "" "Oracle 12c" "Failover" {
                  liveSecondaryDatabaseInstance = containerInstance database "Failover"
              }
          }
          deploymentNode "bigbank-prod001" "" "" "" {
              softwareSystemInstance mainframe
          }
      }
  
      primaryDatabaseServer -> secondaryDatabaseServer "Replicates data to"
  }

  }

  views { systemlandscape "SystemLandscape" { include * autoLayout }

  systemcontext internetBankingSystem "SystemContext" {
      include *
      animation {
          internetBankingSystem
          customer
          mainframe
          email
      }
      autoLayout
  }
  
  container internetBankingSystem "Containers" {
      include *
      animation {
          customer mainframe email
          webApplication
          singlePageApplication
          mobileApp
          apiApplication
          database
      }
      autoLayout
  }
  
  component apiApplication "Components" {
      include *
      animation {
          singlePageApplication mobileApp database email mainframe
          signinController securityComponent
          accountsSummaryController mainframeBankingSystemFacade
          resetPasswordController emailComponent
      }
      autoLayout
  }
  
  dynamic apiApplication "SignIn" "Summarises how the sign in feature works in the single-page application." {
      singlePageApplication -> signinController "Submits credentials to"
      signinController -> securityComponent "Validates credentials using"
      securityComponent -> database "select * from users where username = ?"
      database -> securityComponent "Returns user data to"
      securityComponent -> signinController "Returns true if the hashed password matches"
      signinController -> singlePageApplication "Sends back an authentication token to"
      autoLayout
  }
  
  deployment mainframe "Development" "DevelopmentDeployment" {
      include *
      autoLayout
  }
  
  deployment internetBankingSystem "Live" "LiveDeployment" {
      include *
      animation {
          liveSinglePageApplicationInstance
          liveMobileAppInstance
          liveWebApplicationInstance liveApiApplicationInstance
          livePrimaryDatabaseInstance
          liveSecondaryDatabaseInstance
      }
      autoLayout
  }
  
  styles {
      element "Person" {
          color #ffffff
          fontSize 22
          shape Person
      }
      element "Customer" {
          background #08427b
      }
      element "Bank Staff" {
          background #999999
      }
      element "Software System" {
          background #1168bd
          color #ffffff
      }
      element "Existing System" {
          background #999999
          color #ffffff
      }
      element "Container" {
          background #438dd5
          color #ffffff
      }
      element "Web Browser" {
          shape WebBrowser
      }
      element "Mobile App" {
          shape MobileDeviceLandscape
      }
      element "Database" {
          shape Cylinder
      }
      element "Component" {
          background #85bbf0
          color #000000
      }
      element "Failover" {
          opacity 25
      }
  }

  } }

[simonbrowndotje]

That's correct, yes, because the element style sets the colour to blue:

element "Container" {
    background #438dd5
    color #ffffff
}

If you'd like to change this, I would suggest adding an additional tag to your "external containers" (e.g. "External" or "External Container"), and define a suitable element style. You can either do this manually, or use a short script to add a tag to the containers of software systems marked as external.