Sometimes a style that comes with Illustrator is perfect except for the color or other attribute. Good news! You can easily customize a Graphic Style to suit your needs. Make a shape and add a Graphic Style. I made a circle and applied the Graphic Style called
Tissue paper Collage 2 from the
Artistic Effects Graphic Styles Library. Open the Appearance panel (Window > Appearance if it is not already open). You can see all of the effects, fills, and strokes that make up any Graphic Style in the Appearance panel. Note this style has no stroke, but it is comprised of 4 different fills. Click the arrow beside a fill to see the attributes of the fill. On the top fill, you can see in the screenshot that it has an opacity of 25%. Click the Opacity link in the Appearance panel to change the value. You can open each of the other fills to see their attributes and change their values if you want.