I just opened a can of Sig Lite-Coat clear, given to me by a guy who's been out of the hobby for about 20 years. It's discolored. I'm pretty sure that it's rust color, but I can't tell (I'm partly colorblind, so I can tell it's somewhere between brown and dull red, and that's as far as I get).
It was an unopened can, no signs of dope around the rim and with those nifty clips that Sig puts on their dope cans. But it's old enough that the price sticker says "$5.99".
So -- if I use it for base coats, will it be OK, or might that discoloration migrate up through the finish to bite me later on? I'm applying silkspan now, so I have a ways to go before any color goes on.