I was thinking...
Cleric: varies by domain. Life is W, Light, War, and Forge RW, Arcana, Knowldge and Trickery UW, Tempest RUW, Death and Graves BW
Druid: G, with some U, R, or W for land druids. Moon is R/G
Paladin. W, maybe GW for ancients and BW for tyranny
Ranger. G with R or W touches
Sorcerers. R, hint of B or U. Divine gets RW, Shadow BR
Wizard. U, with some UR (evocation) or BU (necromancy)
Warlock. B, with infernal BR, Archfey BG, and Celestial BW
Bard. UW
I could see Monks as W as well, with hints of R (elemental) or B (Shadow). Barbarian is Red, Rogue R or U, and Fighters could be anything.
As for races: dwarves, half-orcs and dragonborn are R, Half-elves and Elves G, Halflings W, Gnomes UG, tieflings B. No U races unless we add tritons, I guess.