5 Day marinated chicken breast
2 days is usually the max for chicken in the fridge that is officially recommend, 5 days is definitely on the long side.  Pending the sell by date that the chicken had originally.

Color is just the marinade, it's the bacteria you need to be concerned about.  Hard to tell if chicken has gone bad in a marinade.

Good acidic or high salt marinade, you are probably safe.   Really up to you if you want to take the small risk or just throw away.