Most terminals are capable of displaying 16 colors; 8 colors and 2
 different brightness values, some (like xterm) can display more, even
 256 colors.
 .
 The colortest package includes set of utilities to help test how many
 colors a terminal can show. These color settings depend on the $TERM
 environment variable and termcap entry and by adjusting or selecting
 correct values, higher colors may be available. The following numbers
 of colors can be tested for: 8, 16 and 256 colors.