LJJ designed this run as a portrait of the real Arabian stallion, Raingod 166140. The variations are based on the different ways his very white-grey color appeared in different lights, as well as the fact that his base color was chestnut - the pinkies are an attempt to capture his color as a yearling, as he shed his foal coat to "pink". This is not a decorator. Arabians have very black skin, and very very fine summer coats. Take very black skin, put an extremely fine coat of white (grey) hair over it, get the horse very clean - and, yes, you'll have a pearly appearance. It's the combination of the black skin and almost translucent white hair - they are "pearlies" standing out on the pasture! Get them really clean and just a little wet, and you have black pearl. Catch them late in the rose-grey phase, in summer, and you have pinky. All perfectly REAL and realistic horse colors.
From Victoria Zanutto who has the pictured conga: Top shelf left to right: Regular run, darkest on the left going lighter to the right; 2nd shelf - regular run, darker to lighter continuing from the shelf above; 3rd shelf - first 5 on the left, regular run continuing from the shelf above - next 5 are all Pinkies; 4th shelf - first 6 on the left are all Tests, next one is Arist Proof, next one doesn't really belong but he's Raingod color (judge's model from Jubilee 2008) then the next 4 are all Special Edition (LJJ had to go back and paint another 30 models for folks whose orders were lost in the shuffle). They all look similar, but there are differences in hoof color and striping, snip, body shading, eyewhites, and face/muzzle color.
Shown with Mare Rain Goddess: http://www.stonehorseref.com/node/11094 and Foal Raindrop: http://www.stonehorseref.com/node/11570.