I have recently bought a few of these paints after reading the glowing reports by American artists. Graham is a small manufacturer whose range of just over thirty colours has been expanded to 70. Most are single pigment formulations which are much better for mixing purposes. The supposed virtues are a very high pigment content with minimal use of fillers. Honey is used in the paint mixture so it is said they are easily re-wetted and don't crack, even after a considerable period.
Together with two fellow artists I put together an order from the sole UK source W.E. Lawrence of Hove. The colours I bought are Ultramarine Pink, a new pigment PR259, Burnt and Raw Umber both Pbr7, Terra Rosa (PR101), Quinacridome Rust (PO48) and Azo Green (PY129). My friends have several others like Ultramarine Violet Deep (PV15)and Scarlet Pyrrol (PO73). I will report further when we have all used them in paintings. So far just swatches and playing around with them but they do look very interesting.