Add some pasta (about 1/5 if you are using 5 colors) to individual sandwich baggies or glass bowls. Add just enough water to cover the pasta, 2 - 4 tablespoons. Add a few drops of gel food coloring. Swish the pasta around until it reaches your desired color. Add additional coloring as needed. Drain the liquid from the bowl/bag directly down the drain as to not stain a porcelain sink. Rinse the pasta with fresh water and set aside. (I like to place mine on paper towels just long enough to absorb excess moisture/color. If you rinsed the pasta well enough, it won’t stick to the paper towels.) Place the pasta in a serving bowl. Repeat with the other colors.
Add all of the pasta to a bowl and add butter or dairy-free margarine and salt. Microwave on “Reheat Dinner Plate” to warm.
*Seelect Tea food coloring comes in natural as well as organic. To
Make the Color Purple:
Combine red and blue to make purple. Then add the tiniest bit of white, if you have some (AmeriColor makes some). White will make the color brighter. Don't add too much or it will turn lavender.
https://glutenfreerecipebox.com/gluten-free-rainbow-pasta/