Here’s a cross section of hair, you can see the cuticle which is the outer transparent circl, then you have the Cortex with all the dark pigments in them the melanin, and the white centers are the medulla.
Notice the size & shapes of the hairs, the oval ones are more curly and the triangle ones are more coarse & curly.
Melanosomes, these carry the pigment, it’s either Eumelanin (Blue/Brown), or the Pheomelanin(Red & Yellow)
Here are the Melanosomes inside the hair.
Here is a picture of Melanin in the hair, you can see that it’s dispersed unevenly