Sorry for the confusion. Image gauges takes an image and splits it from top to bottom in thirds. The first third is the foreground, and the last third is the background. The middle is the part that is actually changed for the gauge value. Here is an example!
As for hue, unfortunately, there is no way to set the hue color directly, as that's based on the previous color of the image (red at hue 30 is different than blue at hue 30). Instead, I think what you may be referring to is the ability to set the tone of images. Tone lets you set any color as an overlay, but doesn't look as good. But I'll consider adding it in the future! ^^
I see. Thank you. That makes things so much clearer. And yes, I guess I was thinking of Tone. If you decide to add it, that'd be pretty neat, if not that's fine. Nothing a little photoshop can't fix. Again thank you for clarifying the image gauge. It gives me some ideas, as well as not needing to make a separate image for a background, border, etc... It's cool that this was a feature. I must have missed it in the free version.