The scrollable parameter input window allows you to set the color of the ambient light. As with other tutorials, you change anyone of the three color components by placing the mouse over the item and with the left button down, drag the mouse up and down. Note that the alpha value of the color is shown here but is fixed and not changable.
You can also change a selected item (drawn in yellow) using the Up-Arrow and Down-Arrow keys. The amount added to or subtracted from the selected item is fixed within the program. However, a multiplier is also used in making the change. You may adjust the multiplier through the Page-Up and Page-Down keys. Making the mulitiplier larger accelerates the change that is made to the selected item.