feeder mice question

I have just purchased 1.1 adult corn snake. The people I bought them from told me the female will eat 4 adult mice and the male will eat 3 adult mice. Since I bought them on their feeding day that is what I fed them. My questions are should I up the size of prey? and Where is a good place to order healthy feeder mice? Their feeding day will be coming up again on 5-19-12 What is the difference between white, dark and hairless adult mice.

Three, or four, adult mice is overkill.
A Cornsnake only needs ~one~ appropriately sized feed item per feeding.
An appropriate sized feed item is at least the same girth (minimum), as the widest portion of the snake's girth, and up to 1.5 times (maximum) the widest portion of the snake's girth.
See here what I wrote for feeding times of an adult Corn: http://www.faunaclassifieds.com/forums/showthread.php?t=305710

Whether the feed item is black, white, grey, brown, gold, spotted, etc., or hairless, makes no difference.
Although, with the hairless, I imagine digestion may be slightly easier (though, typically, unnecessary) ... &/or maybe handling is better for people who are allergic to mice.

Many pet stores carry frozen mice but the price is, comparatively, high.
A cheaper route is to purchase mice from companies/breeders that supply them. Only thing is that they sell in bulk (i.e. each bag can have a 25, 50, 100 count).
There are plenty of companies to choose from. Although there are more, here are just a few that I have had good/okay experience with:
http://www.americanrodent.com/welcome.html
https://micedirect.com/
http://www.rodentpro.com/
You can also check for local suppliers/breeders.

Thanks for all the info. Today was feeding day and I did feed them only 1 appropriately sized prey.