Good point. I see that symbols are coloured in the theme as _preprocessor_. I don't need to change the filetype settings, but simply can set the desired colour in the theme for the token "preprocessor". Thanks a lot. Issue solve. Still I think it would be a good idea, if the theme bundled with Geany, would also fix this. Having a syntactic element in the same foreground colour as the selection colour, leads to trouble.