We just try to be very careful when coloring, especially with lighter marker colors.
Sharpies are waterproof but alcohol-soluble...meaning they’re meant to blend with the color markers (or any other alcohol-based brands).
Also, be sure to use marker paper! It helps preserve your markers and is a blast to use.
Side note: Try using Sharpies and Crayola markers! Crayolas are water-based so you can color over the Sharpie lines as much as you want, with no bleeding. Although, I wouldn’t recommend Crayolas on marker paper. Watercolor paper is best for Crayolas!
I hope this helps!!!