When I set my Visual Theme to dark from design mode, after my app starts up, applying a scheme doesn’t change any colors, but when my Visual Theme is set to custom, the scheme works as expected. However, the scrollbars are then light instead of dark. I don’t understand how a Visual Theme takes precedent over a syntax scheme.
SOLVED: Setting the syntaxedit VisualThemeType to VisualStudioCode fixed both the lexer scheme colors issue and the scrollbar color issue. The problem I was experiencing is when the theme type was set to Dark, only Some of my lexer scheme colors would apply to the syntaxedit. The idents would remain gray, for example. Setting the theme type to Custom would let all my scheme colors work but then the scrollbar would be white.