update BG colors

I needed a bite-sized task to test my new tools for updating the gallery...so I updated the BG colors to the new color scheme @skrugman created to be more color-blind friendly.

New colors visible in the gallery [here](http://tidepool-org.github.io/tideline/example/jebeck-update-colors.html). I think maybe we should go with more opacity on the hover highlight for the SMBGs - the new colors are more intense. @skrugman @brandonarbiter @ianjorgensen, opinions?