Style lower and upper fill in HTML5 range input

Question

As explained here, IE allows styling of the lower and upper fill or track regions in CSS as follows:

Answer 1

There's a (newish?) pseudo-element for Firefox that styles (what IE calls) the 'lower' part of the range input. According to the documentation:

The ::-moz-range-progress CSS pseudo-element represents the portion of the "track" (the groove in which the indicator aka thumb slides) of an of type="range", which corresponds to values lower than the value currently selected by the thumb.

For the upper track, you still use (per Alexander Dayan's answer) ::-moz-range-track.

I just discovered and tried it today; works pretty well.