I've investigated this too. Most of the alternative glyphs with the word 'colon' in the description are decidedly unattractive as a colon replacement (˸,܄,﹕,᠄,：,︓, and ꞉`).

There is another alternative that at least has a similar character width to the original colon - the mathematical symbol for a ratio: ∶. It looks great in a number of monospaced fonts, but it is a little small in the default MacOS system font.

Here it is being used in a file name:

/Users/me/Books/Book Title: Book Subtitle.pdf [restricted colon glyph]  /Users/me/Books/Book Title∶ Book Subtitle.pdf [permitted ratio glyph]

I've investigated this too. Most of the alternative glyphs with the word 'colon' in the description are decidedly unattractive as a colon replacement (˸,  ܄,  ﹕,  ᠄,  ：, ︓, and ꞉).

There is another alternative that at least has a similar character width to the original colon - the mathematical symbol for a ratio: ∶. It looks great in a number of monospaced fonts, but it is a little small in the default MacOS system font.

Here it is being used in a file name:

/Users/me/Books/Book Title: Book Subtitle.pdf [restricted colon glyph] 

/Users/me/Books/Book Title∶ Book Subtitle.pdf [permitted ratio glyph]