Saturation

/**
 * Saturation. 
 * 
 * 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. 
 */
 
int barWidth = 20;
int lastBar = -1;


void setup() {
    size(640, 360);
    colorMode(HSB, width, height, 100); 
    noStroke();
}


void draw() {
    int whichBar = mouseX / barWidth;

    if (whichBar != lastBar) {
        int barX = whichBar * barWidth;

        fill(barX, mouseY, 66.0f);

        rect(barX, 0, barWidth, height);
        lastBar = whichBar;
    }
}