Shedding only dark hairs

[bdp31770]

I have light brown and have slowly moved from a Norwood 1 to Norwood 2 over the last couple decades. Ive taken Rogaine once a day during this time and started Finpecia in February. I havent noticed much shedding, though when I apply Rogaine, I usually have a couple hairs in my fingers right after, and they are almost always very dark/black.

 

I know that most peoples hair is made up of different colored hair, though am curious if losing dark hairs when someones overall hair color is lighter, means anything. Thank you for any suggestions.