Hair Falling Out — Lighter Color Near Bulb

I am a 21 (about to be 22) year old male and I am currently in between a NW 2 and 3 on the balding scale. I’ve been taking propecia for about 4 months with decent results.

My question is, when I examine hair that has fallen out of my head, it appears that the hair is lighter colored at the base of the hair (near the bulb) than up around the middle and tip. Is this a sign that the hair has thinned or is it normal for hair to be lighter near the base?

You did not state your hair color. In blonde, gray or white haired people, the bulb is lighter. In hair that is near the end of its life, the pigment changes may be lighter in color as is hair that is about to go into telogen. If you are worried about balding, then get your hair mapped out for miniaturization to determine what is actually going on in your hair.