Thanks to Wade and Brian for your comments!
The Bass in South Africa target mainly Bream (Tilapia), Carp and Yellowfish. In certain areas Trout are also present. The profile of the Ospreys would imitate the Carp and Yellowfish nicely and I think Umaxco has come out with a Carp colour which I'll have to consider when I order again! Carp and Yellowfish display similar golden hues.
A South African Bass writer (Charles Norman) commented many years ago in his book that he had quite a bit of success with Bass on small Rapala floating/diving minnow lures in the Rainbow Trout colour pattern even in waters where trout were not stocked and theorised that the lure caught the attention of the Bass by looking "out of place" and in trouble and easier to catch than the natural prey.
At the time he made this observation, Florida Bass were not yet stocked in South Africa, so this was his experience with Northern strain Bass. I know some American writers have at times mentioned that the Florida strain Bass seems more selective or shy in its feeding habits than the Northern strain and that some Floridas would pass up a garish lure not resembling natural prey which a Northern Bass would not hestitate chasing.
I appreciate your comments - quite amazing that we can share thoughts and techniques about catching our favourite fish even though we live halfway across the world from each other!