If you have a corner or turn that makes it really awkward not to change direction, you can either color using curved lines or color using very small circles instead of lines. Just keep in mind that how you color will always be visible and will create the appearance of texture.
Crayon Tinting. Using crayons for tinting embroidery is the most common technique. It's easy to learn and most people have at least a few crayons around. Crayons produce a bold color, but you can also work more gently with them, resulting in a lighter tint. Just like coloring on paper with crayons, varying the amount of pressure and layering your coloring creates some very cool shading. That shading gives your embroidery texture and dimension, and it's fun to use with modern or vintage designs.