leak from oil pump area

I agree with Dave and would also add that some of the common assy lubes are red, and you have to use a good amount to get the big O ring around the pump housing to go into the case opening.
Also fluid can be spilled a little out of the converter when it gets put in.
In other words a little fluid in that area is common when a new trans goes in and it is usually said to run it and make sure it doesn't continue.
Even a spot the size of a quarter on the ground is fairly common at first.

There is a gasket behind the pump, a big O ring around the pump to case contact area AND the sealing washers around the bolts so it's pretty rare to have a leak at the pump area unless the converter pump drive hub is cracked, or the tension spring popped off the seal on assembly.