OK, seriously... that's embarrassing... the slimes last night were about 2-3 screens away from my house at the Necromancer Arena, so I really had no excuse not to see them!!
I'd read that they do "damage" to you, but you don't die (which was one of my concerns because my fisher's not exactly combat-hardened)... well, even in a "safe" location such as the arena, I still found myself OooOOOOoooing fairly soon as I couldn't cure the poisons they'd gotten me with... Olive Green Forest Green and a Dark Grey were the only colors I saw in the area, though.