In English--U.S. English, anyway--"crayons" are, specifically, wax crayons, like these: http://images.fineartamerica.com/images-medium-large/crayola-64-valerie-morrison.jpg They are often given to kids to draw with. "Coloring books" are also popular. They contain line drawings. You use the wax crayons to fill all the areas within the lines with colors. Traditionally, this was a children's activity. In just the last few years, a craze has developed for adult coloring books that have intricate designs. A "crayon box" is just a box full of crayons--either the box they came in, or a larger box. Coloring with crayons forces you to concentrate on a pleasant, simple, amusing task. This takes your mind away from sources of stress. Because the book has line drawings in it, you don't need to be able to draw. Nevertheless, simply choosing what colors to use is a creative task. To "get into your crayon box" means to open up your crayon box, reach in, and take some crayons out. "feel the need to get out of problems and into your crayon box" means "feel the need to forget your daily stress for a little while and concentrate on an easy creative task." The passage might mean literally to get out wax crayons and color in a coloring book, or it might just mean figuratively to escape from the daily routine and do something easy but creative.

Crayon means pencil in French, so I guess it's something about it

Well, not sure if that's a help, but sometimes "crayon box" is used as a term for "crack house" or any place where you can buy drugs. So I have no clue where you found this sentence, but if it has at least a slight chance of being drug related, i'd say the person saying this is suggesting someone else to get high, in order to forget the problems or challenges he's facing at the moment. The structure of the sentence certainly allows the phrase to be used in such meaning, so...

Maybe to let go of your problems and start to be creative (hence painting with crayons, i.e. those coloured sticks of wax or pastels you painted with as a child in kindergarten...)