Quoting myself from Post #304 of the Pencils You May Have Never Seen
Some Procolours are just as awfully fugitive as Artists and Studios. Apparently they never learn - or is it really possible that better pigments would be too expensive? After all Derwent renovated its Watercolour range some years ago and some Watercolour hues are much more lightfast than Artists and Studios. To be honest, the entire Procolour brand seems a little superfluous - they are not that
much different from Artists and Studio.
I totally agree, the whole Procolour range does seem pointless - they are so similar to the Artists range. I've got the same colours (like Heather and Soft Violet) in both Procolour and Arists, and if you use one then the other, it's very difficult to tell which is which. They feel and look the same.
So they go wery well together but Procolours really aren't much softer.