This example is for Processing 3+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.

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