The safari jacket that you choose to take on your dream trip should have some of the characteristics listed below to be as effective as possible...
These guidelines are from my own personal experience and the tips and recommendations stored in the trip reports at African Safari Journals.
1: It should be khaki, olive or brown in colour.
A bright coloured or white garment will make you conspicuous to the wildlife if you are walking through the bush (in a vehicle it doesn't make any difference) and will show up dust and dirt more readily.
2: "Breathable" material with moisture wicking properties works best.
Both synthetics and cotton can be found with the above characteristics. It's not absolutely essential but it will help make you a lot more comfortable in the variable climate that you will encounter in Africa.
Advances in material technology have also brought about the inclusion of things like stain-repelling Teflon coatings and waterproof quarpel finishing's which are a nice to have but shouldn't really be a deal breaker if they're not available on the safari jacket you are interested in.
Most of these outfits come with epaulette's but personally I've never found a use for them in over 100 safaris, so unless you have a specific function in mind they are probably purely decorative.
3: It should be lightweight and machine or hand washable.
Packing space is going to be at a premium so you don't want a very bulky garment that will fill your suitcase to overflowing. Flat packing capability is a big plus.
Dry cleaning facilities are few and far between in wildlife areas so a hand or machine washable garment is essential. With any luck you won't have to wash it before you get back from your trip but it pays to be prepared.
4: Zip off sleeves and lots of pockets are a plus.
Turning your garment into a vest for day use by zipping off the sleeves is a good idea. When it cools down in the evening just zip them back on. The pockets are ideal for guidebooks, photographic paraphernalia, snacks and anything else you need quick and easy access to.
5: It should be warm.
This goes without saying really, but many people underestimate how cold it can get on safari, especially in the early mornings. And if you are travelling in an open safari vehicle the wind chill factor is multiplied, so make sure the jacket you choose has the ability to keep you snug.