https://colemak.com/Multilingual states that the "special characters" section of the layout is "MS Windows/Mac only", but here's a way to have them on X11, too.
You need to pick an unused dead key (eg. "dead_semivoiced_sound") and assign it to the magic AltGr+[\] key:
* xmodmap -e "keycode 51 = backslash bar backslash bar dead_semivoiced_sound"
* or modify the Colemak xkb file and replace the first "asciitilde" on the <BKSL> key by "dead_semivoiced_sound".
Then you need to create an .XCompose file in your homedir to create custom dead key sequences:
# ~/.XCompose
# This file defines custom Compose sequence for Unicode characters
# Import default rules from the system Compose file:
# include "/usr/X11R7/lib/X11/locale/en_US.UTF-8/Compose"
include "%L"
# Colemak special characters
# from https://colemak.com/Multilingual
<dead_semivoiced_sound> <c> : "©" copyright # COPYRIGHT SIGN
<dead_semivoiced_sound> <r> : "®" registered # REGISTERED SIGN
<dead_semivoiced_sound> <t> : "™" U2122 # TRADE MARK SIGN
<dead_semivoiced_sound> <d> : "°" degree # DEGREE SIGN
<dead_semivoiced_sound> <m> : "µ" mu # MICRO SIGN
<dead_semivoiced_sound> <n> : "№" numerosign # NUMERO SIGN
<dead_semivoiced_sound> <p> : "¶" paragraph # PILCROW SIGN
<dead_semivoiced_sound> <s> : "§" section # SECTION SIGN
<dead_semivoiced_sound> <period> : "…" ellipsis # HORIZONTAL ELLIPSIS
<dead_semivoiced_sound> <plus> : "±" plusminus # PLUS-MINUS SIGN
<dead_semivoiced_sound> <equal> : "≠" U2260 # NOT EQUAL TO
<dead_semivoiced_sound> <less> : "≤" U2264 # LESS-THAN OR EQUAL TO
<dead_semivoiced_sound> <greater> : "≥" U2265 # GREATER-THAN OR EQUAL TO
<dead_semivoiced_sound> <asciitilde> : "≈" U2248 # ALMOST EQUAL TO
<dead_semivoiced_sound> <percent> : "‰" U2030 # PER MILLE SIGN
<dead_semivoiced_sound> <bar> : "¦" brokenbar # BROKEN BARYou can pick any other unused dead key (locate keysymdef.h on your system for a list), and you can of course assign it to any key you want (I find AltGr+[\] a bit hard to reach).
Note that on X11, all this is in fact quite unnecessary as you can type all these symbols (and many more!) using standard Compose key sequences, but this way you type them "the Colemak way" and equivalent on different platforms.
