You won't have to worry about the color of your clothes in Southern Africa. if you took at OAT trip to Eastern Africa, where there are tse tse flies, the recommendation is that you wear earthtone colors. You would see that the tse tse fly traps are colored black and blue, because these colors attract the flies. Flies are minimal to non-existant in Southern Africa.
As to malaria pills-we have used malarone for five trips and have never had problems, although on two of the five trips, a few people developed a rash, which was attributed to the medication. a small price to pay for protection against malaria. There is now a generic available for malarone, so it should be even cheaper.
The Grand Circle trip is not as adventurous as the OAT trip, so you likely will not get the same exposure to wildlife, but you will get some. It is recommended, however, that you consider your travel insurance, and purchase a policy with a rather large evacuation benefit, if you need it.