I voted my top 3 out of the 5, which were: Black, White & Two Tone.
Theres nothing wrong with silver alloys but since you usually spend a lot of money on a set of wheels, why not make them different? get more for your money? I think black alloys look good on cars that have black trimmings/bumpers and also if the cars color is a light one.
i.e. Black alloys on a bright yellow car would look nice.
Two-Tone is perfect for the car thats looks stupid with just silver or black. You don't see many two toned alloys around at the moment but I like the way some cars can pull it off.
Same goes for white, I reckon white alloys look absolutely stunning with black cars, blue cars of my favorite: Dark Red cars. As for color coded alloys, Ive seen them around but 75% of the time, its over-done. You see a nice car in say... orange but its been fully color coded (trimmings, bumpers, mirrors) and then to top it all off, it has orange alloys. To be honest, its just a little bit too much and an eyesore.