They can be used on nearly any surface, including unprimed canvas.
Can be made into washes.
Are non-toxic because they are a water-based medium.
Do not yellow over time.
Once applied on a surface, have a high degree of flexibility, therefore adapt well to contractions and expansions of a surface.
Can be used as an under painting for an oil painting.
They have a plastic-like appearance.
Vary from transparent to opaque depending on the pigments.