[santra]

Found it:

Select object
Open Inspector
Go to Style:Fill Inspector
Select "Fill Color" box at top right of fill area in Style:Fill Inspector
This should bring up the Color menu(s)
No matter which Color menu/icon you select at the top--"Color Wheel", "Color Sliders", "Color Palettes", etc.--at the bottom you'll have a slider called "Opacity"
Use that slider to control translucence/opacity of the object