Internal Fan of My Mitsubishi Air Conditioner Has Been Yellowing

The fan blades in my Mitsubishi air conditioner have become discolored. Even though I'm happy with how the air conditioner is blowing, I'm not too pleased with the fact that the fan blades inside have turned yellow. Even though the fan was replaced by the service center before the warranty expired, the replacement material turned out to be low quality, which caused discoloration. I feel really awkward when this issue comes up in front of my guests.