Scintilla colors overwrite to make MySQL Workbench darker than usual.
To use this dark theme, just locate and replace the file code_editor.xml file from your MySQL Workbench data directory by this one. Just remember to make a copy of your file BEFORE replacing it.
_/usr/share/mysql-workbench/data/codeeditor.xml
_C:\Program Files\MySQL\MySQL Workbench X.X\data\codeeditor.xml