(~s)
Note: in AM, use 'watercolor'
1.
Watercolours are coloured paints, used for painting pictures, which you apply with a wet brush or dissolve in water first.
...a collection of rich paintings in ~, acrylic and oil.
N-VAR
2.
A ~ is a picture which has been painted with ~s.
...a lovely ~ by J. M. W. Turner.
N-COUNT