Keep in mind that when you stack items of varying opacities, the colors are combined and may produce a buildup of ink. For example, if you place a yellow box with a 30% opacity in front of a cyan box with 100% opacity, the box in front will become slightly greenish.

You can control this by grouping items and specifying a group opacity rather than individual item opacities. To do this, use the Group Opacity field in the Group tab of the Modify dialog box (Item menu). Depending on the effect you want, you may need to revert the Opacity field for the individual items to 100% (otherwise, each item’s opacity is added to the group’s opacity).

With these three grouped items, compare individual item opacity to group opacity. At left, each item is 50% opaque — the items in front compose against the items behind them. At right, each item’s opacity is 100% while the group’s opacity is 50% — the entire group composes against the background. The items in the group, however, could have individual opacities in addition to the group opacity.