Deffo looks like condensation in the engine to me, it can be a yellow and coffee ish colour. I used to have the same problem with my golf GTI. Its caused mostly by short trips, and happens this time of year a lot when its damp and cold. A few big runs getting the engine stinking hot can help, otherwise dont worry about it too much, just clean the cap now and then (as long as it it condensation that is).....good disclaimer!
ps could also be water in the oil, a sure sign the head gasket is having problems