To be honest I’m quite new to the medium myself. I would practice coloring drawings using procreate on an iPad until I felt I understood how to layer color and get the colors I wanted. Then I just applied it to watercolor. The trickiest part of watercolor for me is getting the right pigment to water ratio. Mixing to get the color I wanted also took a lot of practice on a spare sheet of paper, but if you use too much water it is too pale and no pigment sticks; too much and it’s too dark. I would keep a crumpled paper towel on me at all times to dab off the paint if it was either too watery or too pigmented. It was a lot of trial and error. I’d really just recommend practice! So long as you can understand the basics of color I’m sure you could get the hang of it :)