So... having recently obtained a couple of used copies of TI3, I am considering taking the extra plastics and painting them, then giving each race its own color. The big question is what colors to use for which race. What seems the most appropriate? I was kind of curious what colors other people associate with the various races.

Red -> ?

Purple -> Jol-Nar

Blue -> ?

Green > ?

Yellow -> Hacan

Orange -> Mentak

Black -> ?

Gray -> ?

-------------- New Colors below--------------

White -> ?

Brown -> ?

Gold -> Lazax

Silver -> ?

That's 12 out of 18... thoughts on the other colors and which races they should be matched with?

Well, I can't speak for others, but I do have a digital collection of units coloured for each race (not including Shards), as follows:

Hacan - Yellow (original colour)

Jol-Nar - Deep Pink/Light Purple (new colour)

L1Z1X - Dark Blue (orig)

Letnev - Grey (technically a bit darker than the real grey tokens, but close enough)

Mentak - Orange (orig)

Muaat - Black (orig)

Naalu - Beige (new)

N'Orr - Red (orig)

Saar - Brown (new)

Sol - Baby Blue (new)

Winnu - Dark ("Royal") Purple (orig)

Xxcha - Olive Green (new)

Yin - White (new)

Yssaril - Dark Green (orig)

These colours were picked out prior to the release of Shards and I haven't gotten around to making new sets for those guys yet, but if you've got two copies of the base game and one copy of SE, that should be just enough sets of plastic to match this, if you're so inclined.

Agree with most of Steve-O's suggestions with the exception of:

Muaat: Fluff says their ships are bronze colored. Might as well go with that?

Yssaril: Light green

From there... for the new races of shards...

Lazax: Gold makes sense

Creuss: Silver

Arborec: Forest Green

Nekro: Either Maroon or a sort of Gunmetal color