Color vision deficiency support

[Brian Sperlongano]

          > I think this looks good, but I wonder if we should worry about accessibility for various types of color blindness? These colors might not be an issue, or maybe the presence of labels is enough, but just thought I should flag this before we make too many identical icons in different categories.

Thanks for raising this. Using the nifty tool here: https://davidmathlogic.com/colorblind/#%23F38F00-%23003F87-%23693F23-%23A20067-%234E008E-%23006747 with our current POI colors:

This seems to indicate that orange and blue are essentially always distinguishable. The purple (used for airport features) tends to look blue, while mauve (used for transport features) can look similar to either brown or blue depending on the type of color-blindness (the first two are more common than the third).

Based on this, it might be worth considering changing the shade of blue and/or purple we use. If we implement green icons, care will be needed to make sure they don't look identical to our brown icons. Otherwise, as Brian suggests, we could implement on-the-fly color switching, or clickable icons that display more information (I could imagine a subtitle under the name with the legend entry, for example). But these accessibility considerations might merit their own issue for further discussion.

I still think with some care, we can make distinguishable colors, and the benefits that reusing icons has for style coherence outweigh the downsides of potential confusion.

Originally posted by @wmisener in #1034 (comment)