You just need to richen your high end a click or two. As long as the residue still feels oily, a slightly brownish tint is OK. If it gets really dark brown (burn't oil) or black (metal), you might have a problem. You should check your high speed needle at the start of the day to make sure its set correctly. Changes in temperature can make a big difference in your engines settings. Colder weather requires a richer setting, and vice versa.

Brad