Enter the red, green and blue values for your first colour. Then, enter the alpha (opacity), red, green and blue values for the second colour.
Demonstrates how 2 colours can be alpha blended The formulas are displayed to the right of the screen, but I've also included them in the demo so that you can use them to. Source: http://stackoverflow.com/questions/746899/how-to-calculate-an-rgb-colour-by-specifying-an-alpha-blending-amount
