4. Set a Background Color
Most photographers like to display their images against a black background (or at least a dark background). This is easy: Just select the Rectangle tool from the toolbar (M) and draw a great big box. You have to use either the Swatches panel or the Color panel to select your color.
Because you’re working in RGB, make sure that RGB is the type of color you select in the New Color Swatch dialog box (see Figure 4). To create a new swatch in the Swatches panel, select the New Swatch icon at the bottom of the Swatches panel. Hold down the Alt (PC) or Option (MAC) key so you can select the name and color mode of the new swatch. Give your color a name and make sure that the Color Mode is set to RGB.
Use the Rectangle tool and draw a frame that covers the entire page. When you have your background in place, you can drag and drop your color directly onto the object.
Figure 4 Use the Swatches panel to create RGB colors for a background.