Payne's Gray is a dark blue grey made from a mixture of Ultramarine, Mars Black and sometimes Crimson. It was named after the 18th c. water-colourist William Payne who created the mixture and often recommended it to his students as an alternative to plain black.
Winsor & Newton Artisan Water Mixable Oil Colour is a genuine oil colour made from modified linseed oil and modified safflower oil. This modification means Artisan Water Mixable Oil Colours can be used without hazardous solvents - they can be cleaned up with water. The colour has been formulated to appear and work just like conventional oil colour. The depth of colour, thick consistency, lightfastness, opacity/transparency, permanence and drying times are all comparable to conventional oils. They're especially good for artists who share a workspace or don't want solvents in school or at home. Using the Artisan oils, mediums, and varnish with the range of colours will ensure the resulting combination continues to be water mixable.