I Have Recently Noticed My Feet Are A Black/brown Color

I have recently noticed my feet are a black/brown color on the balls of my feet and my heels, almost like they are super dirty. I have tried every foot scrub and remedy and cleaned them endlessly and nothing is working. There is no pain or numbness and my feet aren't unusually cold. They really just look like they are super dirty without any explanation. Any answers on how to fix it?