Breadth
The share of assets rising over a period — how broad a move is, as opposed to how large.
A market where bitcoin rises 3% and 80 of the top 100 are up is broad; one where bitcoin rises 3% and 25 are up is narrow, with the index carried by one asset. Coinmico's Fear & Greed index uses the share of assets up over 24 hours as its breadth component, and the heatmap shows the same thing as colour.