Shift Pigment

1st-Level Transmutation
Casting Time: 1 action
Range: Touch
Components: VSM (a paint brush dipped in the color you want to dye the object)
Duration: Instantaneous

Target. A Medium or smaller object, or specifically the hair or fur of a creature.

Effect. You dye the object, hair, or fur a color or colors of your choice.

Attack Roll. If the item is worn or carried by an unwilling creature, or the creature itself is unwilling, you must hit the creature with a melee spell attack to affect it with this spell.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, you may cast this spell on an object 1 size larger for each slot level above 1st.

Source: Homebrew

Rulings

Can the spell affect a creature's skin, eye color, scale color, nail color, or other physical traits?: No, the spell is limited specifically to hair or fur when used on a creature.
Does the hair or fur color grow out over time or is it permanent?: The hair or fur color will grow out over time. It effectively acts as a magic hair dye that will not wash out or fade, but it does not rewrite genetics to permanently give you the hair color.

Changelog

Added the ability to affect a creature's hair or fur.