Injector tip condition? Indications?

I pulled my injectors and looking at them had me wondering. When looking at the injector tips, what do the different conditions that they may be in, indicate? Some looked nice and clean and gold colored, some looked silver with a bit of gold, some looked burnt a bit. All O-rings looked to be decent atleast, none torn to shreds. Injector cups all looked to be in good shape. These injectors are stock 300k miles. Just trying to get an idea on if the condition of the tips points to other areas I need to address, it's getting new injectors with new o-rings so if that was the cause, that will already be taken care of.

I would throw the new injectors in and not worry about anything. That burnt look is just carbon build up. Nothen to worry about.