ANSI Colors  
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ANSI escape codes are a standard for in-band signaling to control the cursor location, color, and other options on text terminals. The ANSI x3.64 standard was released in 1979 and later updated by the 5th edition ECMA-48 standard in 1991, ISO/IEC 6429 in 1992, and ISO-8613-3 in 1995.
ANSI escape codes are started using \e[ and contain numeric codes separated by semicolons. The escape code is terminated with an 'm'.

ANSI Color Codes


ANSI Color Escape Sequences


ANSI Color Options


ANSI Color RGB Values

The 24 bit RGB values used for the 16 ANSI colors differ greatly for each terminal implementation. Below is a system that is both consistent and 12 bit compatible.


OSC Color Palette

The OSC color palette is an extension to the ANSI color standard using a modification of the Operating System Command sequence, documented in the Linux console manual as early as 1996. Support has been added by a handful of terminal emulators, most notably xterm. The extension allows changing the default 16 ANSI colors using a 24 bit RGB value in hexadecimal notation.
To send an OSC color palette code one must print \e]P followed by 1 hexadecimal number indicating one of the 16 ANSI colors, followed by 6 hexadecimal numbers to set a corresponding RGB value. Colors can be reset to their default by printing \e]R. The terminal's default foreground and background color cannot be changed.
The default blue ANSI color is hard to read on a black background. To set it to a lighter shade of blue one would print "\e]P43333BB", and to display the updated color one would print "\e[22;34m".

Support
ANSI color support in MUD clients is generally weak. Universally supported codes are 0 and 1, as well as code 30-37.
Terminal emulators generally support background colors as well as code 4, 5, 7, 9, and 22.

Detection
There is no universal standard for the detection or negotiation of ANSI color support. The following methods exist:
By using the TTYPE TELNET option and checking for a terminal emulator or mud client known to support ANSI colors, such as xterm.
By using the TTYPE TELNET option and checking for the -color, -256color, or -truecolor suffix. For example: xterm-color.
By using the TTYPE TELNET option and using the MUD Terminal Type Standard to detect ANSI color support.

Links

If you want a link added, you can email me at mudclient@gmail.com.

Clients supporting ANSI color

Virtually all MUD clients and terminal emulators support ANSI color.

Codebases

Comparison of MUD codebases - Mudpedia contains a list of MUD servers with ANSI color support.

Snippets
256 color parser - Handles ANSI 16 colors and xterm 256 colors.