The Hue function is found under the Enhance menu.
The directions say this about it:
"Vary the percent hue of the image (0-200%)."
That just explains everything, doesn't it?
Well, I'm not going to get too technical either, but I am going to give you examples of the results of using various percentages.
Basically, 0% is near the red end of the spectrum, and 200% goes the other way, towards the violet end of the spectrum. 100% is the original image. Depending on the color scheme of your original image, you may have to go way past the "max" of 200% to reach the blue/violet range. In my example, once I passed 500%, it startd over at the red end of the spectrum, but with a different effect on the image.
R O Y G B I V
0% 
200%
