In a medium saucepan, combine the dry ingredients. In a 2-cup or larger liquid measuring cup, combine the water, oil, and food coloring. Pour the wet ingredients into the dry ingredients and mix with a wooden spoon. Place the saucepan over medium heat and cook, stirring constantly, until the dough pulls away from the sides of the pan and forms a ball (it will be shaggy and messy looking). This should only take a few minutes.
On a lightly greased countertop, turn out the playdough and knead until smooth. Store the playdough in a tightly covered container or ziploc bag. Tightly covered, the playdough will keep for several months.