A quick note that may help with some of your sketches. As you know, RGB is the default color mode for Processing, but there are other modes. It looks like the HSB mode may be useful for some of you that are trying to control color using a single variable.
take a look here at how to change the color mode and also how you can change the range of values it will accept (for example, 0 to 100 instead of 0 to 255)
also look here at descriptions of different color models. Scroll down to HSB/ HSL for a description. For example, you can control the “Hue” by changing a single variable while keeping Saturation and Brightness constant.
Here is a quick sketch I made using the HSB model and mouseX to determine the hue. I’ve set my range to “width” so that the full width of my window becomes the range to change the “H” value in my background color. Both “S” (saturation) and “B” (brightness) are set to “width” (full value, or all the way up). :: HSB_Mouse_tutorial