There have been three different shades of blue on the NSX:
1997-1999 Monte Carlo Blue Pearl - this is a deep, rich "true" blue. It's not so dark that it would be mistaken for black, not as dark as navy blue. In sunlight it is a fairly bright blue.
2000-2001 Monaco Blue Pearl - this is a blue-purple, VERY bright, and similar to the Supersonic Blue that was used on the Integra.
2002 Long Beach Blue Pearl - this is VERY similar to the '97-99 Monte Carlo Blue Pearl; see comments above.