Though the current style for the SmartArt graphic includes colors, you can change the colors by using the gallery that's shown in this picture. The gallery is on the Design tab within SmartArt Tools on the Ribbon. It's in the SmartArt Styles group.
To change the style's colors:
Click Change Colors
, next to the style choices.
Point to any color variation.
Look at the preview on the graphic. As usual, click the thumbnail to apply the colors.
The color choices use the spectrum of colors that are part of the presentation theme. They're divided by row into the primary colors of the scheme, shown at the top, and the accent colors — which on your slides are used for a range of things, such as color fills and hyperlink text.
The Colorful section mixes up the accent colors into various combinations. The rows such as Accent 1 and Accent 2 use shades of one of the accent colors, applied in different ways.
If you change the theme for the presentation, your graphic's colors will be updated to match the new theme.