I'm not sure you can tell the magnet type just by looking, except maybe tell the ceramics from the Alnicos. Any colour differences appear to be very slight. Ceramic magnets are normally darker/greyer than alnico and are supposed to be non-conductive, so you could use a multimeter on then to check it they have a high (ceramic) or low (Alnico) resistance.
For some reason, Alnico 3 doesn't contain any Co (Cobalt) so really is an "Alni" magnet. It's also less powerful than Alnico 2 and only just stronger than Alnico 1 (so really 2 and 3 should have been renumbered in the table). Alnico 5 produces around a 33% stronger magnetic field than Alnico 3, and as the magnet sizes are pretty much the same for a given pickup configuration, that's very much the increase in output you'd get by changing from an Alnico 3 to an Alnico 5 magnet.