RGB Function

red: Any integer expression that represents the red component (0-255) of the composite color. green: Any integer expression that represents the green component (0-255) of the composite color. blue: Any integer expression that represents the blue component (0-255) of the composite color.

The resulting Long value is calculated with the following formula:
Result = red×65536 + green×256 + blue. Under VBA compatibility mode (Option VBASupport 1), the Long value is calculated as
Result = red + green×256 + blue×65536
See RGB Function [VBA] The color picker dialog helps computing red, green and blue components of a composite color. Changing the color of text and selecting Custom color displays the color picker dialog.