A little more detail for anyone who didn't grow up with D&D or any of the billion things inspired by their conception of chromatic dragons:

Red Lair: Reds like hot places; this is one of the trickiest lairs to find, probably, because the obvious choice is volcanic Mount Kiadana-Rah and we did not go in that direction because it's already quite full of crimson dragons. However, I can safely say there's magma in the Red Lair and that hopefully narrows it down a bit.

White Lair: It's somewhere cold. (To the best of my knowledge, this is the only lair found so far.)

Green Lair: It's in a forest.

Blue Lair: It's in a desert.

Black Lair: It's in a swamp.

Tiamat: She used to be on top of the Dragon Tower, and she's still in a high-up place.

Some of the entrances to the lairs are not obvious.

Happy hunting!