Yes, read an RTF tutorial to learn more. Example:

Code:
dialog test {
  title "Test Dialog"
  size -1 -1 500 500
  edit "Test Edit", 1, 5 5 490 490, multi return rich
}
on *:DIALOG:test:init:0:{
  did -ra $dname 1 {\rtf1\ansi $+ $&
    {\colortbl;\red255\green0\blue0;\red0\green0\blue255;\red255\green255\blue0;} $+ $&
    {\fonttbl\f0\fmodern Arial Black;}\f0\fs24\pard\cf2m\cf1IR\cf3C\par}
}

/dialog -m test test