Have a weird rat question..?

anyone with a pet rat knows that his "d*ck" is inside this "pouch-thing" that looks kinda like a belly on.....my rat has a bald mommy, and was lots of inbreeding in his family (not done by me) his "d*ck" is partly out of his "pouch-thing" and is turning purple-ish, instead of the gross bright-red color i know them to be....why is it like this?