Mouth guard turns yellow, is that bad?

Depends: Mouth guards collect bacteria, plaque and tartar may accumulate. Very important to thoroughly clean after each wearing. Hard plastic guards will discolor less than soft, rubber type guards which are more porous and will discolor over time. Be sure to bring your guards every time you have your dental cleaning appointments so that your dentist may check the fit & condition of your guard.

It needs evaluation: If your mouthguard was clear and it has turned yellow it may need evaluation by your dentist. Take it in with you to your prophylaxis appointment so it can be professionally cleaned and evaluated along with you teeth.