before we begin I reccomend you check out my first hair shading tutorial for color selection, as i will not be going over that here, this will be for the back of the hair

Step 1: so using your darkest color make the following shapes in the top corners of the back

Step 2: Using a lighter color than before draw lines connected to the tips of the previous ones you drew your hair should be looking like this currently

Step 3: using your next color fill in between the lines that you have so that your hair now looks like this -

step 4: after step three any additions to the hair are optional, personally I like to add a few highlights to the hair so using a lighter shade highlight the middle parts

your hair should now look like this


step 5 Completly Optional: if you are using PMC skin 3d you will notice there is an option to make the color you are using more transparent, so if you do wanna do a dip dye effect but you're feeling a bit lazy then just ajust the transparency on your color to about 50% and go over your hair it should look somthing like this -