How do I avoid purple-on-black and yellow-on-white?

[Bruce Korb]

I needed to use emacs in a terminal window that was in reverse mode -- 
background black.
I was completely unable to read any of the prompts without highlighting the text
because the prompts are all purple.  Somehow, those two combinations need to be
prevented.  Completely.  Entirely.  Never allowed to happen at all.  It should 
not
be up to a hapless user to figure out how to configure coloration.  It's too 
hard.
Thanks you! :)