Add water, flour and salt to a medium saucepan and whisk together until combined.
Heat over medium heat, whisking constantly, until mixture thickens.
Remove from heat and divide into paint storage containers. Add 3-5 drops food coloring to each container.
Use wooden dowel to stir each bowl to mix color in. Add more drops of food coloring if you desire a deeper color.
Notes
Mixture will stain clothes and skin. I highly advise using art aprons and gloves to protect clothing and hands.
Store in a disposable container or no-spill paint cup with a tight fitting lid. Use within 10-days. Be sure your paint does not have a fermented smell before using. If so, toss.
To make DIY water colors, make the recipe as stated.When you have the final consistency, split another cup of water or so across however many colors you made. Stir well with a spoon to mix. Repeat the process until you get the desired consistency, texture and color you want.