The best known NAS drives are the Red series from Western Digital (WD). These are available in both 2.5" and 3.5" form factors and in capacities of up to 4TB. Whilst around 15% more expensive than conventional drives, this additional expenditure is well worthwhile given the importance of data in a NAS box.
WD now have a complete range of 'coloured' drives. The standard, everyday ones for desktops and laptops are WD Blue. For low energy usage (with slightly reduced performance) there are WD Green drives. For high performance and reliability in file servers, WD Black. For video surveillance and CCTV, WD Purple. Plus of course the WD Red drives mentioned above. Clearly WD do not believe in Henry Ford's famous maxim about the Model T car being available in any colour "as long as it's black"!