What one color provides the best contrast across the color spectrum?

I am trying to figure out what color to use on a floor. This floor needs to be a color that will allow small beads that may fall on it stand out. These beads can be any color from white to blue to pink. What color will best accomplish my goal and could you point me to a website or text that would have research backing it up such as luminescence and other measurements. I was thinking a medium grey but I would like to have some data to support my claim.