transmission lube

[DAK]

Quick question.
When replacing a seal in the transmission, I drained some fluid to that
I could dry out the seal area completely. I noticed it was browner than
I expected it to be. I know motor oil gets quite dark from use. Should I
expect the gear lube to get a medium brown color? Is there any good
reason to replace the factory synthetic stuff at 120K? (yes, I know it
is probably not a bad idea, but...)

David