2x2 L2/L5/L7 color Panorama:

Small (0.5 MB) version
Large (2.3 MB) version
Original (7.3 MB) version
OK, what gives with the coarse, red dirt mixed with the fine gray dust?
Basic question: red drposite first or gray first?
Looks like gray on red to me -- but then why?
grey dust more mobile because it's finer?
Anyone?
These images have corresponding Right views if anyone is interested...