Yes the blue on the 2006 car particularly pretty. That's basically the same blue Red Bull use nowadays and it looks awesome.
The problem with standard Williams blue is it only looks awesome when the sun catches it just right.
The best car i've seen in the flesh recently was actually the FW32. That royal blue was awesome to the eye with the simple white livery. It rarely looked right inm photos and never on TV. My mate did catch it at Silverstone '10 looking awesome though:
There is a shot of Pastor in the young driver test in the FW32 that shows what it actually looked like.