Some colors are more transparent than others. Some colors are very opaque. Test your colors on a separate piece of paper to see how they work together. Too many layers of crayon can make the colors resist each other. This can make it harder to add more color. Use as few colors as possible to get your end result. Scratch out small lines and details (such as hair, the veins in leaves and flowers, etc.) with a craft knife. Crayon is excellent for scratching due to the wax. Do not get frustrated! You will need practice to get the look you want. It's worth it!
For a much lighter effect, you can mix a small amount of soft pastel with baby powder and apply it with cotton balls. This technique is usually used for gradient backgrounds. Lastly, enjoy your work! You can keep it in your portfolio folder or hang it on your wall. There are still a lot of ways to use coloring materials in order to give life to your drawings. Just don't be afraid to explore.