For general coloring,
http://albanach.org/colors.html

Also, we have this concept that coloring in the past was either REALLY bright ("ancient" tones, which are really only "pre-faded") or REALLY muddy (neutrals/naturals). However, there were colorings that were FAR closer to "modern" hues when used. As for the patterns, they also bright/rich and complex tartans (Caledonia is probably the EASIEST to attest from the 18th century and is probably significantly older)
"The Caledonia tartan, worn by any without a clan, was popular in the eighteenth century, but no one is really sure how far back its origins go."
- http://albanach.org/oldtartans.html

So, I think the tones are fine for a reenacting belted plaid.