Sure, it looks like a slab of tripe stuck on your camera, but this Three Colour Pop Up Flash Diffuser looks like a vaguely good idea. The mount clips into your hot shoe holding the pimply bit in front of the flash. It comes in white, orange and blue, just like sunlight, and should help your fill flash approximate the ambient. Best of all, it’s a bargain at US$10.
Flash Diffuser comes with Yellow, Blue and White Colors, which can be suitable for Canon, Nikon, Sony and Minolta.