Click the WordArt object.
Then click the Format tab under Drawing or WordArt Tools.
Then click the Shape Fill button arrow
Click Color to select a theme or standard color.
Click No Fill to remove a fill color.
Click Picture to select a picture file.
Click Gradient to select No Gradient, one of the shadow types, or More Gradients.
Click Texture to select one of the of the texture types, or More Textures.