Keeping crayons and other coloring supplies organized will enable your preschooler to easily put them away themselves. Even children as young as 2 and 3 can learn to care for their own belongings if given the opportunity.
Instead of storing crayons in their original cardboard box or a zippered pencil bag, try finding a small plastic box with latching lid. This is usually a better sized container for little hands. Try finding boxes that stack together well so you can separate markers, crayons, colored pencils, etc. Make sure to label the box clearly and put in a location that is quick to access. Using a storage box will not only make clean up time a bit easier, but also provides an easy access way of using and sharing crayons.
We tend to think that more is better when it comes to art supplies, however, if you keep items to a minimum, they are easier for young kids to manage. You might think that having 5 shades of purple is great for coloring, but with young kids, too many choices can become overwhelming and create confusion about making a choice. Try providing fewer choices and perhaps coloring time will become more exciting and cleanup time will become less of a chore.