[LyX/master] Improve readability of dark text colors in dark mode (#13218)

[Jürgen Spitzmüller]

Am Donnerstag, dem 21.05.2026 um 13:53 +0200 schrieb Jürgen
Spitzmüller:
> Color <light-mode color> <dark-mode color>
> 
> taking the first one for both modes if only one is specified.

Implemented at c962f7b8708f

Expect it to have rough edges.

-- 
Jürgen