Think practical, not fashionable. And the practical reasons are very real.
Colour
Neutrals: khaki, olive, stone, brown. That's not because animals mind colour when you're in a vehicle (they mostly ignore vehicles altogether). It's because colour matters the moment you step out of one, and because bright white shows every speck of dust within an hour.
Two specific tips. Avoid dark blue and black: they attract tsetse flies, which live in parts of Tarangire and the western Serengeti, and their bite is genuinely unpleasant. And avoid camouflage patterns, which civilians aren't allowed to wear in Tanzania and several neighbouring countries.
Layers
The temperature swing across a single day is what catches people out most. A cold dawn, a hot midday, a cool evening. A fleece and a windproof jacket over a shirt covers all three, and you'll be peeling layers off through the morning, not putting them on.
Evenings
Long sleeves, long trousers and closed shoes after dusk. Again, it's all about the mosquitoes. And don't worry, camps aren't formal. Nobody dresses up for dinner in the bush.
If you're walking
A walking safari changes the answer. You'll need proper closed shoes, long trousers to protect you from thorns and grass seeds, and neutral colours stop being a preference and become a rule.