First time I emptied mine after about 3600 miles, I got about a shot glass full of black fluid. As 180 notes, hopefully you're not getting coolant in the oil. Check the dipstick oil to see if it's also tan colored. Could just be condensation from cold weather or short trips. Here's a post from another forum with the same issue:
Milky Brown engine oil??? - Dodge Challenger Forum: Challenger & SRT8 Forums