Indeed the current colors are a bit strong. I obviously liked the paler type of color from the earlier version. This is more of an attempt to make the captions and text more readable for the dark mode users. That white font on pale background is not looking good, as pointed out by Ñuño Martínez.

I still haven't tried/managed to force the font to black so this is a mitigating attempt.
The hope is that though the colors may be a bit strong at least most user can read the letters and better see what's going on and what's to do.

Using a RadioGroup for selecting difiicutly is an interesting idea. I generally like using the available Lazarus components, when possible. Why invent the wheel again when so much userful stuff is already available?