Histogram Data Driven Colors

[nofurtherinformation]

Histograms should be able to show color scaling based on values using data driven properties, the same as scatterplots.

[stuartlynn]

This is partially resolved.

We need to think a little more about how this should work. Scatter plots have the ability to show colors easily because each point has the full set of variables available to it. Histograms however only have the aggregate values for each bin. We could make it so that the colors are based on a second column with some aggregate applied within the bin, so bin values of A colored by the sum of variable B within each of those bins.