The arena I used to show at had white arena walls... Those horses, I remember one who looked like he had stood in paint up to the elbow and was otherwise brown, actually looked really funny going around the ring. Horse with no legs.... was a little unsettling!
This I think is an example of shade variation within the color. We see this in Blue Point Siamese . . . you can have Blue Points with an (undesirable) buff or brown tone to the blue color. I have one little Blue female who has very pronounced buff shading to her blue color -- my big Blue male has the true slate-blue tone, and if you put them side by side it's obvious.
They're pretty, but I think the website's assertion that it's only a matter of time before AKC recognizes the color is just whistling in the dark. You couldn't show those dogs.
Of course, they'd be perfectly good for anything else you wanted to do, so long as their hips and eyes are good and they don't have temperament problems. That's the problem with breeding from a restricted gene pool - especially in the first few generations.