Select the drawn object on the page.
Left mouse click on the None button 
on the colour palette. This will cancel the fill for the drawn object, in other words, if you had drawn an object with a fill, the fill will disappear.
All objects drawn with the Opus drawing tools can have an outline and fill.
You can set the Fill colour before you draw the object or you can change it afterwards by selecting the object and changing the current fill colour. The fill colour can be a single solid colour or you can create a gradient fill colour. Alternatively, you can have no fill for a drawn object.
Double-click the Draw object on the page – this will open the object’s Properties dialog.
Select the Background tab in the Properties dialog – see Background tab for more information.
Use one of the fills in the Styles option or create your own gradient fill, then click the Apply button to save your changes.
Select the Draw object on the page.
Right mouse click your chosen colour from the colour palette. The fill colour box will change to the colour you selected.
If the colour you require is not available, double-click on any empty colour well. This will bring up the Colour Selector dialog box and allow you to create a custom colour.
Select the drawn object on the page.
Left mouse click on the None button on the colour palette. This will cancel the fill for the drawn object, in other words, if you had drawn an object with a fill, the fill will disappear.