A not-so-useful visualization that uses a quadtree to bin a lot of points in square cells. Each original point has a third numerical value, which is used to color it. Bins are also colored, according to the mean value of contained points.
A pattern, which has been artificially introduced into random data, can be seen from the gradient of color. There is a correlation between the value and the x coordinate.
The result is not that informative, because it fails to represent the density of points (i.e., the amount of points in a bin). Color could have been used to convey that information, but there are techniques better than binning to do that (e.g., smooth interpolation and/or contour lines). Perhaps contour lines could be added to this diagram to help.
https://d3js.org/d3.v4.min.js
https://d3js.org/d3-selection-multi.v0.4.min.js