RE: set the highlight color when searching

[Drew Adams]

> > [X] Foreground: white      (sample)
> > where "sample" is blue colored! The "white"
> > didn't take effekt. Why?
> 
> some hours later I made some further tests:
> green works, black, too! And red also, but not white and 
> yellow!

`M-x list-colors-display' will show you some colors you can use.  
When I do that, `white' is one of the possibilities.
If it is a possibility for you too, then try again.

The `custom-set-faces' entry added by Customize to your .emacs says that your
Emacs must support at least 8 colors for that entry to have an effect:
`(min-colors 8)'.

What happens if you edit the face in Customize as you want, then set that
change, and then in the same Emacs session you use isearch?

(Works for me.)