RGB is the Red, Green, and Blue color model, which allows you to set the red, green, and blue values of the colors you wish to produce. The RGB color model is an "additive" model. When 100 percent of each color is mixed together, it creates white light. From the Color Chooser window, select the RGB tab; and the RGB tab (Figure 1) becomes available.
There are two ways to adjust the red, green, blue, and alpha value of colors. There is a slider bar for Red, Green, Blue, and Alpha. Alpha controls the opacity of the color. As you change the slider bar for each one, in the Preview field, the color you are producing is shown. Another way to affect the color is you can directly enter a value in the Red, Green, Blue, and Alpha cells. Click OK, and the Color Chooser window will close. Depending on where you accessed the Color Chooser window, you will have to click either Apply or OK for the color change to appear in the display area.