erm, make a perfect circle, then make a radial gradient of the same colour but going from a lighter version of that colour to the colour you want, use the gradient tool to drag it out from the area you want then clip it to the circle.
Then make an oval (this is gonna be the light reflecting on the top) and make it a white (at the top) to black gradient, place it at the top where the light should be and set this layer to screen.
It will now look like a ball :)