Sure, thanks, but that only answers the periodization part (and Wikipedia might not always be accurate).
I am looking for uniform reference in two types:
1) period photos of units involved in fighting
2) color reference in form of photos of original items, reenactments and modern illustrations.

Hello. I am making a video game "Comrades and Barons: Cards of Bloody 1919". The game is based on events of the year 1919, centered around all the fighting that went on in Latvia with different armies clashing for different goals. It is intended to be a Hearthstone style card game. (links ...