Variable characters per step in progress bars?

[josswright]

Apologies if this is something I've missed, but I can't find any mention of it.

Is it--or would it be!--possible for a progress bar to have different characters for current, incomplete, and complete at each step?

A couple of potential uses I see for this:

• a progress bar that runs in a gradient from red to green as it progresses;
• a progress bar that can record success or failure (or other statuses) at each step

(This could be interpreted in two ways: one would be that a character is set when that step is passed, and remains fixed from then on. I suppose another option would be that certain completed characters could be variable and be retroactively updated with each update.)

I feel like I might just be missing an obvious option or reference somewhere, but I can't see any documentation or examples that mention this; everything just seems to pre-set static characters for current, complete, and incomplete.