Colored MUDs are split into two varieties: the type where the very first thing it asks is whether you want ANSI color; and the type where it goes straight to the main login screen, which is NEVER coloured regardless of color preferences.

And yet it is possible for the MUD to determine, without the player even being aware of it, what MUD client the player is using, and thus whether it supports ANSI.

But ANSI is just one example. Others would include determining whether the MUD should provide an artificial local echo, or whether the arrow keys get sent as characters (windows Telnet) or whether they are function keys for the client itself which never make it to the MUD (zMUD).

The vast, overwhelming majority of MUDs use the telnet protocol (even though the vast, overwhelming majority of MUD owners do not even know what the telnet protocol even is). The telnet protocol allows hidden client-server dialogues which the end user does not even see, which allow the server to determine many things, one of which is what type of program the player is using to log on (ie, their mud client).

Most MUDs, however, merely ignore this awesome capability, and if the client initiates one of those hidden dialogues (to ask whether it should use local echo, for example), most MUDs merely gag it and ignore it, without responding.

These days, alot of kids and teenagers do not know what "ANSI" is. If the weird text-based game is trying to solicit this info from them (which is totally unprofessional since, as I've shown above, it is unnecessary in most cases), they'll just say "screw it" and go play Everquest.