It's true that you'll rarely find a correspondence between a college
team's mascot and its colors.  Usually, a team's colors are chosen for
other reasons than "what are the colors of the animal that we've chose as
our mascot?"  For example, the City of Pittsburgh's colors are black and gold,
so Pitt's colors were chosen as a variation on that, blue and gold.
 
Some schools had colors before mascots.  The Ivy teams were originally
identified by their colors, and still are to some extent.  Hence the
plethora of color names in the Ivies: Harvard Crimson, Cornell Big Red,
Dartmouth Big Green, Brown...well, it's the Bruins.  Princeton uses Tigers
to match its distinctive colors.
 
There are exceptions to any sort of theory you try to propose, unfortunately.
I don't really know what the colors are of Delaware (the Fighting Blue Hens),
but I can guess.  Are Colby's colors white (White Mules)?
 
Minnesota definitely does have a correspondence.  A gopher looks like a gold
squirrel, sort of.  Throw in a whole bunch of students of Scandanavian
descent and you've got "Golden Gophers".  (I always kinda liked thinking
that the mascot name was chosen because there are so many blondes at the
UofM!).
 
Enough of my blabbering.  Gophers, Gophers, GO BIG GOLD!!!
 
-Martin