leaks,Rear axle question

My vehicle has about 55K miles on it. About a month ago, I noticed it was leaking gear oil from underneath the rear differential. The leak is small. I went to change the rear differential fluid, but noticed something while I was underneath: The seal around the axle on the right side is leaking a little, then dripping down onto the differential's lowest point. I'm going on vacation next week, and we know a mechanic close to where we're staying, so we made an appointment.

My question: Assuming the fluid is leaking from the axle seal, is it gear oil from the rear differential? Becau