@cormullion I like how you implemented this, except for the &Post. It really tends to mess up a lot of other kinds of evaluations. However, with a few filters added I could make this very workable. ty.

This 'stretches' the hue gradient over the entire string of digits, rather than displaying each character with a specific color. Not quite what I had in mind, but still interesting, especially with much longer strings.

@m_goldberg This works for what I had in mind. Thank you.

@Jens Residue is interesting but it won't work for my purposes. I just want to essentially replace denominators that are 0 with 1. Because this step is 'in the middle' it probably does seem kind of dubious. When you're working with pencil and paper it seems extremely simple, but telling the dang machine how is maddening.

@Nasser I was wondering why all the different combinations of Hold, HoldAll, HoldForm, etcetera were not working.