Q: Something that looks to be oil coolant mix under my 2006 audi a6 quattro. I bought the car drove it home and its been parked since

Something that looks to be oil coolant mix under my 2006 audi a6 quattro. I bought the car drove it home and its been parked since. Initially it was just a little oil dripping here and there so I bought some oil to replace the loss and ran the car for approx. 20 min the next day is when I noticed what my brother says is a coolant oil mix under the car where the oil was initially dripping. No check engine or warning lights and when I drove it home it seemed to drive just fine. Please help, it's hard to pin point due to the car having a cover on the bottom of the car covering underneath the engine. Hoping/praying this isn't expensive.

My car has 111000 miles.
My car has an automatic transmission.