stumped me then.

still sure there is no way for brake fluid to get into the car, especially on both sides.

could imagine maybe passenger side if its run down the servo bracket and the gummy sealant used between that and the body had leaked. but its far fetched.

it must be coolant, its the right colour and both footwells. Have you checked where the heater pipes go through the bulkhead? theres a metal plate with a gasket, maybe its leaking and running down the inside of bulkhead. could happen if the pipes havent made a good enough seal on new matrix. Check it from engine bay. could be easy case of slopping some instant gasket about if old foamy rubber gasket has failed.

I know mine was perished beyond belief!