[thristian]

For what it's worth, there's a lot of 24-bit-capable terminals that aren't MacTerm. Even xterm supports the 24-bit-color sequences, although it picks the closest entry in its 256-colour palette rather than using the 24-bit colour directly.

Also, you seem to be assuming "xterm" supports 256 colours and everything else doesn't. The best way to figure out how many colours the terminal supports is $(tput colours). tput also looks up other useful sequences; you can "tput bold" to turn on bold mode, "tput setaf 12" to set the foreground to colour 12 (bright yellow), "tput sgr0" to zero all active formatting, etc.

[makecheck]

Good point. Although, unless there are shells that have "tput" built-in, that means more subprocesses to obtain basic information (which would slow down the result a bit). In my case, the environment is sufficient to figure out what to do.