The title asks as this text is optional but were they Red/Black flags in the dark ages probably speaking about 900-1450s Before 1500 were they always black and red or is it my minimal understanding of rebellions during that time. By rebels I mean peasant and ones that demand claim of the throne.
Thanks in Advance :D
The situation you are describing may exist in a computer game, but there is no historical corollary. That is, whatever situation the game is depicting never actually happened, and there is no historical answer to the question. Our understanding of rebels in the "dark ages" is not 'minimal', but there is no such thing as a standard "rebel flag".
Is this question inspired by the Paradox Plaza series of games?
The red and black flag you're thinking of is the anarcho-syndicalist flag, which likely came out of the Spanish Civil War. Paradox uses it as a generic rebel flag in all of their games, no matter when they're set. There's no evidence of anything like it from the middle ages, and its symbolism is rooted in modern concepts of anarchism and socialism.
In fact, there was no single design for "rebel flags" during the time you're talking about (which remember is six hundred years of history). Some uprisings did have specific flags associated with them, like the sixteenth-century Bundschuh movement, which was named after the tied shoe on their flag. But that wasn't by any means standard.
This image of the English Peasants' Revolt (which was made around a hundred years after the fact) actually shows rebels using what we might call royal symbols: the royal banner of England, and a square St. George's cross flag. Other illustrations show rebels flying non-descript banners or no banners at all.
