The Fill Tool
The Fill Tool is selected from the Image Toolbox. The Fill Tool behaves differently depending on the currently selected Fill Tool Options.
The Fill Tool Options
1. Solid fill: Will fill the selected area with a flood of one colour, the “ink” if the left button is used, and the “paper” if the right button is used.
2. Gradient fill: Will fill the selected area with a smooth gradient.
To apply gradient: Click on area to fill, hold button and drag the guide.
It’ll fill the area with a concentric pattern of gradient, from the ink colour to the paper colour whose radius is equal to the length of the guide, and whose centre lies at the beginning of the guide.
Right clicking will reverse the order of the gradient.