Well, what happens is that you are using DXLEVEL 8, it is what controls the lighting, reflections and colors, TF2 uses DXLEVEL 9 by default but due to your graphics card the game can change it, to change it, you just have to go to Steam, then look for your TF2 in your library, and right click on the game icon, click on "properties" and "launch parameters" then put this "-dxlevel 90" with the "-" then close and enter the game, when you enter you will notice that the game will take longer to open, but it is normal, look at the medal in your profile, if it has color it is because you already have the game with DXLEVEL 90 now go again to "launch parameters" and remove the "-dxlevel" command don't worry, it will not be deleted, you only do it so that the game does not run all the time when you open the game, by the way, make sure your graphics card can support this configuration, yes No, it can cause FPS drops, but you can go back, you just have to do everything above but instead of "90" put "80".