The Winsor & Newton student ranges include colours labelled as "hues" (for example: Cadmium Red Hue, Cerulean Blue Hue, and Cobalt Blue Hue). These are colours that have been made from an alternate pigment to approximate the original colour at a lower cost; the real difference is in how they perform. When comparing the genuine Cadmium Red with its hue counterpart, you'll see that they're both a bright red. Both are very permanent but the cadmium is opaque while the hue is transparent. Don't dismiss the hue as lower quality, because of its natural transparency and mixing characteristics, some artists may prefer the hue colour!

~Excerpted from "The Oil Colour Book" by Winsor & Newton