Saturation is the strength or purity of the color and represents the amount of gray in proportion to the hue. A "saturated" color is pure and an "unsaturated" color has a large percentage of gray. Move the cursor vertically over each bar to alter its saturation.
barWidth = 20
def setup():
size(barWidth * 32, 360)
colorMode(HSB, width, height, 100)
noStroke()
def draw():
whichBar = mouseX / barWidth
barX = whichBar * barWidth
fill(barX, mouseY, 66)
rect(barX, 0, barWidth, height)