Most likely what you are seeing is the carbon stringers right under the base giving a slight off coloration. Hard to know for sure with out pictures though.
Probably right. However my Revolver doesn't have any marks and I can't say I've ever seen any that way.... I didn't notice it on an Evo I just looked at a couple days ago either, but who knows.
"When I do good, I feel good; when I do bad, I feel bad. Thatís my religion." - Abraham Lincoln
Moral of the story: If your going to rob people, wear a diaper.