There's an issue with the color compiler that is included in VS 2022 Preview 3 (it has already been fixed for upcoming Preview 4).
If you see this error:
Microsoft(R) Visual Studio(R) Vsix Color Compiler version 16.0.0.4.
(C) Microsoft Corporation. All rights reserved.
Could not load file or assembly 'Microsoft.VisualStudio.PkgDef, Version=16.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
System.ApplicationException: Fatal error running VsixColorCompiler.exe
at ThemeConverter.Program.CompileTheme(String deployInstall) in C:\Users\huvalo\source\repos\theme-converter-for-vs\ThemeConverter\ThemeConverter\Program.cs:line 134
at ThemeConverter.Program.Convert(String filePath, String pkgdefOutputPath, String deployInstall) in C:\Users\huvalo\source\repos\theme-converter-for-vs\ThemeConverter\ThemeConverter\Program.cs:line 107
at ThemeConverter.Program.Main(String[] args) in C:\Users\huvalo\source\repos\theme-converter-for-vs\ThemeConverter\ThemeConverter\Program.cs:line 69
WORKAROUND
Open this file in a text editor like notepad as administrator
There's an issue with the color compiler that is included in VS 2022 Preview 3 (it has already been fixed for upcoming Preview 4).
If you see this error:
WORKAROUND
Open this file in a text editor like notepad as administrator
<vsinstalldir>\VSSDK\VisualStudioIntegration\Tools\Bin\VsixColorCompiler.exe.config
Change this line
to