Here's a way i colour my art.
TheArtistic_Division

Step one is to make your outline of what you want to colour

Step two- pick like 4-5 colours for each part ( hair, eyes, etc.) then pick the lightest colour and Colour it in.
(OR IF YOU WANT CHOOSE ONLY ONE COLOUR FOR EACH THING AND JUST SHADE REALLY LIGHTLY WITH IT! :D)

Step three- take a darker colour and start doing the medium shades for your image (or if you're lazy like me use the same colour but put more pressure on it to get the medium shade

Step four- now use the darker ones to get the shadows and stuff. ( have fun with it)

Step five- add more colours for contrast or blush or stuff... ( make it your own and have fun!)

Hope this helped at least a little lol
Enjoy! :D