That is Subaru sealant that's been used at the dealer level. That's Threebond 1217B and at one time was the Subaru recommendation for transmission pans as it is particularly suited to ATF. It's VERY hard stuff - we call it the pink concrete..... some dealer techs liked it because it rarely leaks.
1217b has been superseded by 1217h for all applications. 1217h is grey.
GD