Diversity index of the contiguous United States by block
Pure blue is maximally segregated (diversity index of 0). Pure yellow is maximally diverse in race and ethnicity (diversity index of 0.8 or more). Colors in between are linearly scaled in between. Blocks with no population are not plotted. Thanks to mlinksva for color suggestions.
Block level data from Census 2010, calculated as described in the Census 2000 Diversity report except that the Public Law release of Census 2010 did not go into further detail about the racial identification of people who identified themselves as Hispanic. It is a pretty high bar to have 8 categories equally represented in a single block.