Mouse hair pigment cells move between different parts of the hair follicle and change their state back and forth, which is linked to WNT signaling.

WNT signals in the hair follicle are linked to pigment cells turning into mature color-producing cells in mice.

Skin cells around the hair follicle make WNT signals that turn on WNT activity in pigment stem cells in mice.

When mouse hair starts growing, pigment stem cells in the hair germ turn on color-making and branch-related genes before they divide.

When mice experience sudden stress, it causes the cells that give hair its color to panic and leave their home in the hair follicle, burning out too soon and making the fur turn gray forever.

When mouse hair is repeatedly plucked, more pigment cells get stuck in the bulge area (from 10% to 50% of follicles), and these stuck cells don't help make new hair color.