set_color can't use all "ANSI" colors on background #1464
Description
I've been trying to create a somewhat dynamic theme, that would instead of hardcoded hex values refer to the terminal's own "ANSI" colors.
However, it isn't possible to use a bold/bright variant (the latter 8 of the 16 palette) as a background color with set_color.
Screenshot example:
Expected results: the "bold/bright" variant of green should be the backround color in the third and fourth line. Instead, third line does not work at all, and fourth results in bold/bright foreground and the background is the "normal" green.
On foreground (the first line), it is possible to access the "bold/bright" variants of ANSI colors specified by the terminal.
Suggestion: allow referring to "ANSI" colors with color0-color15 or something similar, instead of relying to -o / --bold, or alternatively, allow -o / --bold parsing also for the background colors.
(spacecolors.sh borrowed with <3 from here)