Paint > Setting Brush Attributes and Modes > Brush Attributes >

# Brush Opacity

The brush opacity affects the transparency of the brush. A value of 100% applies a fully opaque colour. Use a lower value to apply a more transparent colour. Enter a value in the Opacity field.

(a) Current Colour field

NoteYou can only use the Front, Back, Result, and Saved attribute modes with the Opacity attribute.