It would be cool to visualize the depth with a colormap that makes it visually possible to compare depths, e.g. Matlab's Hot. HSV colormaps are pretty but make direct visual comparisons difficult [1].
Yes, this is not intended to be a visualization; it is merely something pretty. D3 supports Lab and HCL color spaces [1] which are perceptually uniform; I could use those to improve the accuracy of the distance encoding, but I’d have to sacrifice the current garish aesthetic.
[1] http://people.renci.org/~borland/pdfs/RainbowColorMap_VisVie...