Many states use color to represent levels of Covid-19 and/or county restrictions. The color scales states use vary across the country. For The New York Times, Caity Weaver details the usage and the challenges of picking meaningful scales.
Varying colors of state guidance maps
Second Edition
Visualize This: The FlowingData Guide to Design, Visualization, and Statistics (2nd Edition)
Visualize This: The FlowingData Guide to Design, Visualization, and Statistics (2nd Edition)
New tools, refined process.
