implement colorblind mode

[cooperq]

Closes #77

[wgreenberg]

just the one comment, though i do worry about calling it colorblind_mode when it only addresses a single colorblindness type. probably fine for now, but as we get more users, we'll probably wanna work on this more.

[cooperq]

just the one comment, though i do worry about calling it colorblind_mode when it only addresses a single colorblindness type. probably fine for now, but as we get more users, we'll probably wanna work on this more.

looking at simulations I think just switching green to blue should be about enough to differentiate the color change for most types of color blindness. The more obvious thing might be something like a dashed line I guess but I worry about that being noticed by someone inspecting the device.

[wgreenberg]

lgtm!