In this case, you only need 3colours.
Step1:
Use the lightest colour to outline the shape and separate the hair zones.
Remeber to sharpen your pencil to make the lines thin.
Step 2:
Fill all basement colour.
Step 3:
Use the darker colour to highlight some area.
Step 4:
Use the black or darkest brown to refine the dark area.
Final:
Use black colour to finish the head colour and some shadow area.
Done
your tutorial is very helpful and your doing great with drawing and I'll be glad to hear your opinion about it here is the link and hope you'll like it :)
https://steemit.com/art/@othmanesl/harry-potter-drawing