I was talking with an instructor this afternoon, and we noted the following about previewing mathematics expression input. If one previews something like (sin((x+1)^2)/3)(x+2), the display of the answer may show up with various sized parens, etc., to show what the meaning of the expression is.
Extending this further, we wondered if the previewer could do something like display the independent variable(s) in a different color, e.g., blue. Similarly, one "could" color other parameters. In that I use jsMath for previewing by default, this would require that the jsMath renderer be able to figure out what the independent variable(s) is(are) for the problem, and be able to color the occurrences of the independent variable(s).
My understanding is that jsMath uses either local fonts, or downloaded images, to create the display. Thus the second part of this, it seems, would depend on either being able to use colored local fonts or to have different color font images.
In any event, if anyone has thoughts about the desirability or feasibility of this, I'd be interested to hear them.