This is a question I get a lot when I teach.
The true definition of hue is colour. In a paint name, it means that it is the colour of that particular pigment, but it is achieved by using another pigment of similar hue.
This can be because the original pigment is obsolete and needs replacing, but because artists are familiar with its name, paint manufacturers want to continue using it. For example, Alizarin Crimson is an old pigment that fades when exposed to light. But we love our Alizarin, so the new version is still called Alizarin Crimson, with the addition of “hue” (or sometimes “Permanent”, as in Permanent Alizarin Crimson) to the name. The process is still in progress, as the old Alizarin is still available.
Another reason to use a substitute pigment is if the original is expensive and the manufacturer want to create a cheaper range of paints. This is the case for the Cadmiums. Red Camium Hue is the colour of Cadmium but it contains no Cadmium. As far as I am concerned this is a good thing as I banned Cadmiums from my palette many years ago. But for Cadmium fans, in this case “hue” means “fake” and is a bad thing.
I have recorded a video that explains all of this in detail.
You can watch it here:
If I don’t have the time to write another post before then, I wish you a beautiful Christmas and a creative, healthy and happy 2020!