The only 'color-theme' Ive been able to use so far is to set background to
wheat.

I am now trying some more attractive (aka darker) color themes

Now I have

(custom-set-faces
 '(org-hide ((((background light)) (:foreground "wheat")))))

which is done to hide stars in org mode. [That's a fearful number of '('s
even for an ol-lisper!]

I would like to generalize "wheat" to "whatever is the background color"

How is that done?