256 colours, that means working in the lowest mode called 8-bit. A CV64/3D can work also in 15 bit, 16 bit and 24 bit. But 8-bit works the fastest if you have an 68030 like I did on my former A1200 tower. But if you want lotsa colours without overloading the processor then just use 15 bit which will display most gfx very good ...
In these days of A4000's with PPC turboboard and PCI busboard it doesn't mean that we will drop you just because you have 'only' an ancient A2000 !!! It is still a system that is capable of being upgraded with modern hardware, from Buddha/Catweasel to 2060 turboboard !!
Besides, you have got a 68040 card inside which is more than most A1200's have. You only need a gfx card to have an up to date system. Do you also have got an IDE controller inside ?? Get an Xsurf ethernet card which also has got an IDE controller so you can connect ultra cheap and mega fast CDroms !!