To make the scrollbars control the color of the background displayed, you will need to first define one additional "public" method to handle scrolling events. The event handling interface requires that you use the name "scroll" for this method. This method will be invoked by the browser each time any of the scrollbars you created in "begin" is changed by the user. The browser will not pass it any parameters. So, its header should look just like the header for "begin" except for the name.
Type a header for the "scroll" method between the "begin" method and the background drawing method already contained in your applet. After the header type two lines with matching braces to contain the body of the method.
All you need to do when the user changes a scrollbar is redraw the background. You already defined a method to do that. So, all you need to include in the body of the "scroll" method is a single line to invoke your background drawing method. The tricky part is figuring out what parameters to include in the line within "scroll" that invokes your background drawing method.
The values you pass as parameters should be those corresponding to the positions of the scroll bars after whatever the user did to cause the browser to invoke your "scroll" handling method. As you write the applet, you can't know what these values will be. Since the "scroll" method has no parameters, you don't have any names for them either. Fortunately, the "Sliders" themselves are capable of telling you their current values.
If "redControl" is the name of one of your Slides, then the method invocation:
will tell you the current setting of the Slider. You should use three such invocations to specify the parameter to your background drawing method within the "scroll" method.redControl.getvalue()
When you think you have it write, run the applet, move the scrollbars and see what happens.