Woro-woro (shared taxis) cost between CFA300 and CFA800, depending on the length of the journey, and vary in colour according to their function. The yellow taxis work like minibuses, going from one designated spot to another across town; they're usually shared, and do not drop people off to individual destinations. The challenge is to know which one goes where – you'll have to ask.
The red taxis are usually hired just by you (unless you choose to share) and will take you pretty much anywhere within Abidjan. A short hop in a cab from Le Plateau to Zone 4 costs around CFA2000.
If you want to hire a taxi driver for a day, bank on anywhere between CFA15,000 and CFA30,000, depending on the strength of your negotiating skills.
Note that licensed taxis are not allowed to leave Abidjan's boundaries.