A few related statements per Magpul....
Magpul
Product Updates
•With the launch of Stealth Gray across the board, we will be discontinuing Foliage Green as a color option, to be completely phased out by the end of 2014. Also, based on demand and to maintain consistency across our line of magazine products, all non-black MOE magazine color options will be discontinued by the end of 2014.
•Black is very hard to beat in strength as a color. This is due to the small size of the carbon molecule which makes up the black color and disruptes the base material the least during the molding process.
Sand color came about during experimentation in new materials and processing. It was the first time we made a color that was as strong as black but it took another couple of years of development to get a color that kept the M3s strength but fell within the new US Army "non black" specifications.
Technology is not static, it evolves.
•This new Sand colored material shares many of the properties and components of our latest black material. Endurance, reliability, chemical resistance, stability, and other parameters are exactly the same. The main difference, due to some proprietary developments in composition, is strength. The GEN M3 AR/M4 PMAG is extremely resilient in black. However, as tough as our basic black material is, the Sand material is even stronger. We’ve seen very significant increases in feed lip drop and other rough handling tests from -60F to 180F—to an extent that it made our initial results hard to believe. Similar proportional increases in the other magazines in our line have been seen in our testing. With this increase in drop strength, we still see the resiliency that makes the PMAG what it is—Feed geometry does not change, unlike metal or softer polymer magazines—and so reliable feeding is not affected by this punishment.