I don’t know about brake cleaner. It is a hot aggressive solvent and probably not the best stuff to put on our frames.
DOT-3 and 4 brake fluids are hygroscopic which means they readily absorb water. Wiping it with a dripping wet rag within a few seconds may have prevented the discoloration.
Wipe the Whole fram with it..........then it will match...
I have thought about this for a while because I have stains on my frame also. I just havent figured out what to use that will NOT cause the PC to peel.