The trick is to have enough distinctly different shades to work with, and to mix up where things land. Boots, hats, pants, shirts, vests. Five parts. Three browns, two tans, a blue, a gray, black, and a white, for instance, will let you do nine figures' pants without repeating once.
Mix it up. If figure A gets brown 1 for the pants, and figure B gets tan 2, then do figure A's shirt in tan 2 and don't use brown 1 on figure B (or just use it for his boots.)
Tans, browns, and grays (wool) were most common, but clothing, especially for the middle class and up, was still often colorful. Red, blue, green, and white were popular (white for the well-to-do, unbleached muslin for the working class - more of a cream.) Red, green, and blue calico (the cloth, not the pattern) wasn't uncommon in the lower classes, either. It was usually a duller tone than the wealthy's - perhaps a bit of brown or gray into the base color to dull it. Blue denim for pants was extremely popular among workmen in the late 19th, so feel free to use blue jeans. You don't want a rainbow, but don't be afraid to skip some jackets, vests, or shirts to add some color in the late 'uniqueness' pass where you paint each one with something special to make them stand out.
Make sure that similar looking sculpts get painted differently - if you have to repeat one of the tans, do it on two dissimilar looking figures, not on two that look the same (for instance the two guys in tophats holding bottles in your photo are very similar.)
As an aside, I've never heard of the 'outside-in' technique. Most people do the opposite - they start with the skin, then 'get dressed' from the inner layers out.
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