select the object whose colour is to be changed.
right-click on the object and choose "Properties" from the menu.
choose to change the fill colour or the outline colour from the dialog.
press the colour button and the following dialog is displayed:
left-click in the multi-coloured window and select the desired colour by moving the mouse.
release the left mouse button.
left-click (and hold) on the small triangle next to the shaded-grey window to the right of the multi-coloured window.
select the desired brightness by moving the mouse up and down.
release the left mouse button.
the colour may be saved in the Custom Colour palette by clicking in one of the custom colour squares and pressing the Add to Custom Colors button (this is optional).
press OK.