on uniform colors

[exequiel]

hello, i am new to your forum. i am physician in our country and during my spare time i usually build scale models. lately i have been giving some thought on doing scale figures, particularly on legionaries.

i have seen illustrations/ pictures over the net and i noticed legionaries don't always seem to have red over their armor/ shields. does this mean some legions/ units have color coding? if so, is there a list that cite which colors were worn by which unit?

thank you in advance