A simple way to emphasize the effect is to replace one of the initial explosion frames with a white matte frame. Though it displays for a split second, the white frame helps convey the action. Once an ignition has occurred the fuel burns. The speed and intensity at which the fuel burns usually defines the force of the blast. In essence an explosion is a lightning fast burn.
Different fuels have different burn rates and generate differing amounts of heat.
This is something that also can effect the color of an explosion. One thing that can help define the scale of the explosion is the definition of the fire or smoke. The more detail, the larger the explosion. The motion of the fire or smoke is also important. Fast moving flames usually tell the eye small scale, yet a large fireball will linger and burn much longer, billowing out slowly.