For the record, Decker uses a 4-bit palette configured from a 24-bit gamut: http://beyondloom.com/decker/color.html

Reflowing UIs to suit varying aspect ratios is a challenging puzzle that Decker presently doesn't touch, though I do have some ideas for the future. If decks were embedded as inline "applets" of interactive content within a fluid document container (markdown, gemtext, etc) I think reflow would be considerably less important.