Curiostiy Question

Question
I've had my pet rat for about a month and a half now.  My boyfriend bought him for me at a pet store for Valentine's day and his exact age is unknown.  When we asked if we could see all that rats the women looked at us like we were crazy. And when we told her we wanted it for a pet she looked at us like we were even more crazier.  She let us hold him in the store to make sure he was tame enough to become a pet and of course he was. I have him in a wire cage and the bedding is Carefresh Pet Bedding, but I cut up old material and old wash clothes that he likes to sleep on.  In the mornings I feed him pellets, a small piece of cracker and a vegetable, which his favorite is peas.  Then he normally gets a snack around lunchtime (piece of bread and peanut butter).  And for dinner he normally gets some pellets and a variety of other vegetables.  He gets all kinds of attention from me and my boyfriend.  He's gotten to the point of when he hears our voices he runs around his cage jumping up and down until we talk to him.  We take him out a few times a day and normally let him run on the couch.  He runs back and fourth on the top of the couch and normally stops and watches the fish swim around. At first I thought he would run away, but he hasn't even attempted to do so. My question isn't major, but it was more of a curiosity question.  When we first got him his fur was tan.  Just a few days ago he developed this black/gray spot  by his nose.  I was just wondering if his fur wasn't fully grown or what it could be.  Also I read how male fur becomes oily.  I was wondering if you could tell me what type of rat shampoo was best to use on him.

Answer
Is it JUST on his nose? If so, I'm betting he's a "tri-mese", which is a siamese rat essentially. In about 4 months he'll probably be completely molted out into siamese coloration.

I use an oatmeal, unscented, tearless puppy/kitten shampoo on my ratties. Works great, and its cheaper than "rat shampoo" -- same stuff basically :)