To replace transparency with a colour matte:
- From the Edit menu, click Matte.
- From the dialog, choose one of the following:
- Custom Colour—pick any colour from the adjacent swatch using a pop-up HSL Colour wheel.
- Primary Colour—uses the currently set primary colour from the Colour panel.
- Secondary Colour—uses the currently set secondary colour from the Colour panel.
- (Optional) Reduce the Opacity to limit the colour strength.
- Click Apply.