NOTE: All of these steps must take place on the same layer.
You have to name the layer. Example: Blue circle
changecolor1.gifchangecolor1.gif
On the layer 1, draw any shape you want.

changecolor2.gif
Then right click anywhere on the flames and insert key frame.

changecolor3.jpg
Select the shape that you draw and change color.

changecolor5.gif
Choose subselection tool on the side bar and select layer 1.

changecolor6.gif
Look at the properties tool bar and change tween to shape.