Visualizing 28 different variables with 28 different colors?
This is the best solution I have come up with, I simply found a larger color pallet. The largest I could find was:

http://bl.ocks.org/aaizemberg/78bd3dade9593896a59d

So I merged d3 catagory 20 with the first few from d3 category20b which was inspired from this heatmap tools heatmap tool's source code: