Chromatics Dragons have become some of my favorite NPCs to use in campaigns. Currently the group has a Young Purple Dragon with them that they need to help get through a dungeon to destroy the source of a demonic curse that is turning any scaled creature, included said dragon and the party’s Tortle Barbarian, into mindless crystallized husk (kind of like the red lyrium from Dragon Age Inquisition). They are having fun having him crawl along the walls while holding Rogue/Monk of the party and using the dragon’s telepathy as a silent walkie talkie.
Rainbow Dragon is from Dragon #146, "The Dragon's Bestiary" article. Prismatic Dragons are Epic Dragons from the Epic Level Handbook for 3.0E; I was only able to find three of them, and they're in their own grouping, as that's how 3.0E defined them.
Rahab comes from Dragon #062 (June 1982), a two-part article by Pat Reinken providing stats for Ahi, the Steel Dragon, and Rahab, the Grey Dragon. They're two individual dragons that don't fit into the draconic classifications in the 1E Monster Manual, to provide some monkey wrenches for DMs to throw into their games and surprise their players who've memorized the MM! They're decent NPCs IMO, and if I ever ran a dragon-centric campaign I'd probably use them.
In reading the yellow dragon versions in 1E, 2E, and 3.0E/3.5E, they look to be mechanics updates of the original 1E version; the 4E Draconomicon doesn't have a Yellow Dragon. Is there something I missed?