Opus provides a simply palette of basic colours from which to choose colours wherever this is required in the program, such as when you want to choose a background colour in the Background tab of an object’s Properties dialog box. Below is an illustration of a drop down colour well:
At the bottom of the drop down box are two special options to allow you to choose colours not currently provided in the palette. The Custom button will open the Colour Selector dialog box, while the Colour Picker button allows you to match any colour visible on screen.