From experience, I can tell you: Anything in proximity of the flash will tend to reflect. If it is a color other than black, i.e., white, blue, or red, the flash will reflect those colors and provide a white, blue, or red haze over your photo. What is needed is for the material in proximity of the flash to be non-reflective black, just like the lens shades that are provided with SLR lenses these days.