The notation |G : H| denote the index of a subgroup.

The notation [K : L] denote the index of a field extension.

For these usages the proper Unicode symbol is ∶ (U+2236 ∶ RATIO) that is a little higher up than the normal colon.

MathJax and LaTeX default space around : is equal, but MathML default regard : as a punctuation so left space is thinner than right space. Also, should preserve := and do not change it := (Do later: better if could change it to ≔).

Fix

To output U+2236 by default, and output normal colon by LaTeX code \colon In postfilter for nodes which node value equal :, we set its node value to : and set lspace=0 and rspace=0.
Replaced / with ∕

Modification

Search 
new y.CharacterMap("remap",null,{"-":"\u2212","*":"\u2217","`":"\u2018"})
replace with 
new y.CharacterMap("remap",null,{"-":"\u2212","*":"\u2217","`":"\u2018","/":"∕"})