Tranny fluid in the coolant looks like rusty scum. You may have a cracked radiator. Both the water and tranny fluid run through it in different passge ways. Pull your tranny dipstick and see if the fluid is "normal"
If you don't have coolant in the oil then it'* unlikely you have oil in the coolant. Trans fluid is a bit more likely. Check the trans fluid and flush the radiator to see if it comes back. Could be rust. Was it filled with premixed?