Understanding colors in zsh

Question

In this thread, yoda suggests the following solution for using colors in zsh

#load colors
autoload colors && colors
for COLOR in RED GREEN YELLOW BLUE MAGENTA CYAN BLACK WHITE; do
    eval $COLOR='%{$fg_no_bold[${(L)COLOR}]%}'  #wrap colours between %{ %} to avoid weird gaps in autocomplete
    eval BOLD_$COLOR='%{$fg_bold[${(L)COLOR}]%}'
done
eval RESET='$reset_color'

Correct me if I am wrong, but if I understand correctly, autoload colors && colors allows you to call colors by their name, while the rest of the script just wraps them in ${ $}.

This made me think about the following questions:

1. Is there a way to know what colors are loaded by calling autoload colors && colors?
2. How do I know what colors are supported by my terminal?

Solution

The colors function records the names of colors and similar attributes (bold, underline and so on) in the associative array color. This array associates names with terminal attribute strings, which are numbers, e.g. 00 ↔ normal, 42 ↔ bg-green, …

echo ${(o)color}

If you want to see how the array is built, look at the source of the function: which colors or less $^fpath/colors(N).

The colors function only defines names and escape strings (in the associative arrays fg and bg) for the 8 standard colors. Your terminal may have more. See this answer for how to explore what colors are available.