Firstly, each language service could use its own styling and therefore you'd need to work with whoever wrote the language service to resolve this. However if they are relying on the standard coloring built into VS, which they should, then you usually can change it via Fonts & Colors
. If it isn't available there then you may have to step out to the theme editor and edit it there. Most things are configurable, but not everything.
To figure out what to change you need to find out what the decorator is that is being used. I'm guessing that this is an interpreter warning, an analyzer notice or a quick action notice. I'm guessing it is an analyzer notice. Try changing the coloring of Suggestion ellipses
in Fonts & Colors
. This is what backs the ellipsis for the analyzers.