Citadel Naggaroth Night Base paint is designed to give a smooth, solid dark purple color over an undercoat and for that reason this will almost always be the first paint you use on a miniature. Shake the dark purple paint before using (you can make this easier by adding an agitator ball).
The dark purple paint can be a bit thick sometimes and then you just add a few drops of water to your pallet. You really don't need a lot of water. Something to watch out for is to make sure you don't apply too much paint so that you don't start to hide details.
Another important functionality of this dark purple paint is that it not only covers the undercoat, but also covers other colors. So if you later miss something about this color, you can easily paint over it with this Naggaroth Night base paint.
The color of Citadel Naggaroth Night (21-05) is similar to: Old Citadel Imperial Purple; Vallejo Game Color Royal Purple (72016); Vallejo Model Color Royal Purple (70810); Instar Dark Purple; Reaper Master Deep Amethyst (9079); Coat D'arms Amethyst Purple (160).