Use this menu option to replace areas of a selected colour on a bitmap layer with the current primary colour.
button on the
Design Tools toolbar is a shortcut for this menu option. The availability of this button and toolbar is license dependent
To use the Flood Fill tool:
.
in the
3D View toolbar is toggled on.
over the colour you want to flood fill with the primary colour, and then click. The block of colour on which you click is replaced with the primary colour.