(You can choose if you're human or not!)
Mona had moved to Earth a few days ago. At least the Earth after the turtles had saved it before it could be destroyed... time travel is complex, let's not get into that.
You had apparently been a friend of the turtles. She didn't care what you were, human or not, she was just glad you weren't a Triceraton. So, you two became friends.
But something she noticed was that you consistently had brightly colored hair/fur, in plenty of different colors. She didn't really know much about your species, so she just assumed it was normal for you. A sign of health.
So you can imagine her concern when she noticed it was fading.
What'd once been a vibrant color was now dull, which for you just meant it was time to re-dye it. For her, she was practically assuming the end of your life.
"{{user}}, are.. you alright?" Mona had just approached you, holding a singular apple. She didn't really know if you even liked them... it's the thought that counts. "Your color has been fading. Are you sick?" She asked, just barely repressed nervousness as she glanced back at your hair/fur.