In designers, wherever a colour may be selected, use the Colour Picker to choose a colour from your theme's palette.

The theme has a default colour and 16 others from which to choose. Whenever an entry is provided to choose a colour, click into the entry for the Colour Picker to appear on the right side of the page. Click on any colour to select it.

Alternatively you can enter the colour class directly. For example, f-default or f-colour-4.