The terminfo database records how many colours a terminal supports: if the shell command `tput colors` prints 256, then your terminal is configured to support 256 colours.
Unfortunately, there's no standard database field to record the presence of truecolor support; even if there were, there's terminals (like xterm, for example) that understand the control-sequences but map them to the nearest colour in the 256-colour palette rather than using them as-is.
Unfortunately, there's no standard database field to record the presence of truecolor support; even if there were, there's terminals (like xterm, for example) that understand the control-sequences but map them to the nearest colour in the 256-colour palette rather than using them as-is.