In a medium size bowl add flour, cream of tartar, and salt. Stir to mix.
Carefully add the cup of warm water and oil to the flour mixture. Stir until dough forms. If the dough is too dry, add a small amount of water. If the dough is too wet, add a small amount of flour until desired consistency is met.
Separate the dough into four equal amounts, and place into the additional bowls.
Add 5 - 10 drops of food coloring and mix/knead with your hands. Continue until all the play dough is colored.
Notes
Store each batch inside a zip top bag or containers with lids to keep the dough soft longer.