There are 2 schools of thought:

1. Drab colors: Like in the movie "Braveheart." This fits the notions of camo. It has been noted that the reference to the prominace of brown belted plaids DOES NOT mean they were brown tartans. They may heve been SOLID brown. This tonal range fits what we "expect" to have been worn. It fits popular imagination of "dirty" past.

2. Bright: If you look at many of the fragments and portraits from the pre=Colloden days, many were in bright tones. Red is an especially prominant tone, as are blue and purple. Actually, if you look at many of the Wilson's of Bannockburn tartans, many are purple. Today, most would say that such tartans look way to bright and "unauthentic," but these are VERY easy to defend from actual material and pics.

My BPs are from BOTH sides.
My older ones (the oldest 2)-> are olive based. One has brown and navy (the pattern seen in Greenville games-> the "Jedi" tartan) and the olther has bright blue, yellow, and red stripes on a ground of olive (it sounds odd, but looks nice-> but is HEAVY material 22 or higher-> never measured it).

Others are brighter, including a black watch with a yellow band on the sevage (actually saw something similar in a portait somewhere) and a Dress Gordon.

So, historically, BOTH tonal ranges are acceptable.