Change Red Square to Yellow
Now that we have our colors selected we need to find a tool that can easily swap out the colors for us. The Color Replacer covers all of one color with another by using the foreground or background colors, depending on whether you click the left or right mouse button.Select the Color Replacer tool. (Be careful not to confuse it with the Color CHANGER tool located in the Flood Fill tool flyout.) The tools option palette is like the one you used with the Paint Brush with one important exception: The Tolerance setting. Tolerance controls how much of one color is being replaced with another color. If you set the Tolerance to zero (0), the replaced pixels must match the specified color exactly. Setting the Tolerance higher changes colors that closely match.
Double right click the red square. This will replace the red with the same color of yellow used in the triangle. This was at a tolerance setting of 20, which allows for a small outline to stay around the shape.