I just recently got a issue where my FiveM got overwhelmingly bright. I have no graphics packs installed, I even reset my PC and its still happening. I have tried everything the average support person would tell you. I have searched YouTube and no on seems to have this issue.
you can edit the brightness of the game within the graphics settings, unless your talking about white rooms being very white, that would be under shadows or reflections in graphics.
For anyone still with the problem, Shader settings fixed this for me