I'm not necessarily disagreeing with you, but here's some relevant explanation of their color choices which largely seem to have been chosen for consistency wit

I'm not necessarily disagreeing with you, but here's some relevant explanation of their color choices which largely seem to have been chosen for consistency with previous publications: http://pubs.usgs.gov/sim/3292/pdf/sim3292_pamphlet.pdf http://pubs.usgs.gov/sim/3292/pdf/sim3292_pamphlet.pdf Page 10, search for the word color.