Construct ANSI colour codes

[pauline-galea]

I need ideas on how to construct ANSI colour codes, without hard-coding
them.  Would really still need some scheme such that the actual selection
is human readable.  Perhaps a function that returns you the format string.

Example of scheme

'd' for dim, 'n' for normal
'Gn' for Green, 'Rd' for Red, 'Bl' for blue

'dGn' for dim green foreground

'Bl_dGn' for blue background and dim green foreground