Chameleons under stress will turn black at times, as well as when they are cold and they are trying to retain heat. I have had chameleons turn black after shipment to me as well, and after they have adjusted to their new surroundings and feel safe and warm again, they retain their normal coloration. Give him some time. Black colorations are definitely due to stressful situations, as well as turning black to absorb heat into their body.
It is weird, but I've heard stories about all the carriers and some areas have better luck with some than others. I have had customers tell me that "x" carrier delivers the best for them, and have had other customers in other areas tell me the exact opposite about the same carrier.
For me, here in Maryland where I live, UPS is always right here every day at the same time, whereas DHL is "iffy." And then, other customers tell me, UPS is hardly ever on time here, DHL is best for me. I guess it depends on the reliability of the particular service you get in the area of which you live.
Double edge sword I guess with these guys.
Give him time to relax, some nice hydration, food and let him adjust without bothering him much for a few days to remove the stress. This will help.
