Quality Matters. Not all colored pencils are the same. Cheap colored pencils tend to have harder wax leads and less pigment which mean they produce less vibrant colors and have a tendency to leave some white spaces uncovered in the grain of the paper. Because the lead is hard, cheaper pencil leads often have a tendency break and if the lead breaks throughout the length of the pencil you can be left with something that is unusable.
How to Crayon Tint. To crayon tint, your embroidery, start by transferring your design to the fabric. I recommend using a finely sharpened regular pencil, as it won't require water or be affected by ironing. Place the fabric in an embroidery hoop so the back of the fabric can press against a flat surface and color the design as desired.