How To Blend Colors On Illustrator

The Isolate Blending option in the Transparency dialog (Window>Transparency) helps create blending effects between specific objects rather than the entire document. Users often apply the command to the wrong item. Here we'll go through a few steps to illustrate how you can be sure to apply the blend modes to the objects in the group and Isolate Blending to the group itself. [If you want to download the Illustrator file to follow along, download it here.]

Use Isolate Blending to limit the effect of an object's blend mode to other objects that are grouped with it. This is often used when an object overlaps items in the document that wreck the effectiveness of its blend mode. For example, you may create a pleasant effect by using the Multiply blend mode on objects, but when the items are placed over a background, the effect becomes too dark. Here the color effect is created using the Multiply blend mode. The art looks great on top of white, but when placed on top of the background art, it becomes too dark.

Let's fix this.

1

[ Selecting the objects ]
Select the objects that will get the blend mode and apply it by selecting the mode from the Transparency palette. If you've already grouped the objects in question, select them with the Direct Selection arrow so that you are certain you apply the blend mode to the object and not the group. Select the items and choose a blend mode from the Transparency palette. In this example, the objects all have 80% opacity. When set to Multiply, the objects darken where they cross.

2

[ Grouping the objects ]
Select the objects that have the blend mode and those that you want affected by it and choose Object>Group. Don't forget that grouping objects moves them next to each other in the stacking order. Here the Layers palette shows clearly that grouped items are next to each other in the stacking order.

3

[ Customize blending options ]
With the entire group selected, click the Isolate Blending checkbox in the Transparency palette to isolate the blend. The effect of the blend mode will be limited to items within that group. Now objects in the group only blend with each other.

4

[ Final view of your project ]
Here's the art on top other objects. Now the darkening effect doesn't include the other objects because they aren't grouped to the airplane art.

Tips:

Don't forget that groups themselves can have blend modes and opacity. This can be in addition to the effects the group's members have.
Watch out for applying both Knockout Group and Isolate Blend to the same group. The results may cancel each other out.
Blending in general tends to be more forgiving in RGB mode. For example, in a CMYK file, blending colored objects against grayscale may result in an unwanted knockout effect.
Blending spot color art typically converts it to process color.