Hello Darkshaolin,

Thank you for your feedback, To answer your question, it depends how realistic your cartoon character will looks like. If you want a cartoon like with a soft human skin, then, the best is to use photo references to ease the process. If you are planning a pure cartoon skin, then, it will be easier to paint directly. If you are choosing the second option, then, you can create an image in a photo editor with all your skin tone variation, load it as a reference image to pick colors easily,

Hope it helps,

Best regards,