With shader when I put on some armor like vest and gas mask etc. its like purple and black box how can I fix it

Is it optifine?

do you know how to solve this?

Is it optifine?

yes

No, this is Optifine's problem. Optifine is closed source so I have no way of fixing this - they hack into a lot of Minecraft's internals so generally end up breaking a lot of mods. I suggest trying something like sodium or chlorine.