I have to agree with DrDerekDoctors, it doesn't look much like an explosion except for the colour choice. The central white area remains the same size and just the red outer edge seems to grow and then shrink back. Also, its very uniform in shape, explosions/fire/smoke etc don't tend to be. (However, uniform explosions can work in some types of game) Try making the whole explosion grow in size and dissipate, and use the palette to make it brighter as it explodes, and then darker again as all that remains is smoke and debris.
Here's an explosion effect I did some time back for a game I was working on as an example. Probably not the best example, but its the best I have lying around.
-Z-