In a medium saucepan over medium heat, combine water, all-purpose flour, olive oil, cream of tartar, and desired amount of food coloring.
Stir continuously for 4-5 minutes. The liquid will become firm, pull away from the pan, and form a ball.
Remove the dough from the pan and set it onto a sheet of parchment paper to cool.
When the play dough is completely cool, wrap it tightly in plastic wrap or store it in an air-tight container.