Green is the obvious monster choice. I mean, green is associated with slime, ickyness, reptilian alieness, mold, decay, Mountain Dew and other horrible things. It's also the color Lord Cthulhu is most frequently represented as.
I like the way you're thinking on assigning monsters to the green lined bag.
Blue is usually thought of as peaceful and dignified. It's the color of a tranquil sky or a newborn. It's also associated with police, a force for order and civilization so long as you aren't in Innsmouth.
Additionally, my initial thinking was that elder signs are blue and that's what gets used to seal gates. But … that's also the color of doom tokens on the flip side. Still, many good arguments for assigning the investigator standups to the blue lined bag.
I find your ideas intriguing and would like to subcribe to your newsletter. Seriously though, I just thought I'd start this thread to have a little light hearted fun with folks on the forum. Thank you for playing!
(the stars are right … )