Hue

Hue is the color reflected from or transmitted through an object and is typically referred to as the name of the color (red, blue, yellow, etc.) Move the cursor vertically over each bar to alter its hue.

from p5 import *

barWidth = 20
lastBar = -1

def setup():
        size(640, 360)
        stroke(255, 160)
        color_mode('HSB', height, height, height)
        no_stroke()
        background(0)

def draw():
        global barWidth, lastBar

        whichBar = mouse_x / barWidth
        if whichBar != lastBar:
                barX = whichBar*barWidth
                fill(mouse_x, height, height)
                rect((barX, 0), barWidth, height)
                lastBar = whichBar

if __name__ == '__main__':
  run()