I have a Peace dollar that I think has toned but is really ugly. Pinkish brown. What causes coins to tone and why different collors?

Toning is the same thing as tarnish - which you are probably familiar with - and, on silver is caused mostly by the reaction of the silver with sulfur (found in the air and other places).

The colors are basically the way the light reflects off the toning. Many colors can be formed depending upong the heaviness or thickness fo the toning.

Kind of related but I think you may enjoy checking out this topic.

http://coinpeople.com/index.php?showtopic=665

Shows the various ways coins can tone and their colors. Quite interesting.

I wish I had a pinkish-brown Peace dollar.

Dont clean or bother that coin!!!! It may look ugly to you,but alot of collectors includeing myself look for really nice toned (Natural)coins!but also, there are badly toned ones that suffer and wont be sold, its called "Eye Appeal", Do you have a scanner on your pc?? maybe you could show us some of your Dads coins??

And then you get collectors like me, if it ain't white or toned some shade of grey then i don't want it.

Us collectors are a funny bunch, all very different. And you can never please every collector.