Interestingly, I just found out about the full-width colon.
Full-width :
Normal: :
Note that both of the examples above are a single character. Because it's not the normal colon, you can use it in folder and filenames. It blew my mind when I read how a guy uses it to help him visually organize his filenames.
To anyone who stumbles on this, the 'Full Width' colon is Unicode character 0xFF1A. Windows Character Map doesn't include this particular symbol so it can be impossible to find.
One trick is to launch Microsoft Word or Write (aka Wordpad), type FF1A and immediately press Alt-x. The Alt-x keystroke switches the character before the cursor between unicode and four hex digits (and back).