A color picker
The Garmin (at least my Garmin) is only capable of displaying 6-bit colors.
I found a website that lists and displays a 6-bit color palette, but it’s hard to see how those colors relate and compare to one another in a grid.
Color is 3 dimensional, so I put them into a cube.

Hovering over a color reveals that layer of colors. This makes it much easier to find adjacent colors and see what my Garmin is capable of displaying while designing watch faces.
