Create a graph that contains all the histograms of each color component for foreground and background. There would be two columns: foreground and background. and there would be as many rows as color spaces.
Same format as 1, but instead of histograms, we can output the histogram describing variables. Like mean and standard deviation.
For each color component we output a number. This would represent the distance from the background histogram to the foreground histogram. (I like this one better).
There are various ideas with this: