Colour fade issue

Use the Get Support link at the top of the page here to contact Apple Support. If you have an Apple Store close by, use this link to make a Genius Bar appointment to have the hardware examined by Apple. They will explain your options. Genius Bar Reservation and Apple Support Options - Apple

You described that the blue color of your iPhone case is faded, am I correct? The iPhone is hardware. Apple would need to examine the device to determine what the problem is. I don't believe your warranty will cover that, but only Apple can definitively answer that question.