I've seen several blogs and websites with instructions about dying noodles. I decided to make some for the kindergarten and 1st grade classes at VBS, and they loved them! I divided up the noodles in plastic veggie trays, so the kids could reach them.
Hemp string (it's stiff and strong which makes threading much easier)
Rubbing Alcohol (this sets the color so they don't bleed and noodles keep their shape and firmness)
Put the desired number of noodles in a sandwich baggie. Poor in about 1 - 2 tablespoons of alcohol. Add a few drops of food coloring. Seal the bag, swish around the liquid until all noodles are coated. Leave in for 5 - 10 minutes, until desired color. I poured the noodles into a colander and reserved the dye. Dry the noodles on a paper plate. It might take a couple of hours to dry.
Repeat process for as many colors as you like.