Did you know Adobe Illustrator has a Color Guide to help your design project. By selecting a base color that you want to work with you can generate a harmonious color scheme through the drop down. Once you select the scheme that you want to work with you can use the automatically generated color group by adding it to your swatches, or you can make your own group by choosing the different colors that are displayed. When your satisfied, select your entire artwork and press the apply color button.

Intro to Illustrator: Color Guide Panel