Ask yourself these questions:
are you playing on a game boy color, GBA, or an emulator? Because if you are, the game would be color, but it shouldn't be all red.
where did you get it? Was it a reliable source? Was it used?
If you got it used, Most likely, it's a hacked cartridge hacked to be in red coloring. It could have other affects on the game, like if they changed anything so it look like some kinda creepy pasta. I if the previous user hadn't changed the Pokemon sprites or the story, at all or too much, you should still be able to enjoy a good game of Pokemon. I don't know a way to fix it. Look at Flame-Red's answer below for that.
Overall your game is hacked or changed in a way I don't know about.
Hope I helped!:)