Draw crap on your Novation Launchpad. You'll need the unimidi gem. You know where to get it.

launchpad-art.rb

# USAGE
#
# Make sure your launchpad is plugged in.
#
#   $ ruby launchpad-art.rb
#
# Select your launchpad from the list of midi controllers, then start pushing
# buttons on your launchpad.

require "unimidi"

OUTPUT = UniMIDI::Output.open(0)

class Event
  def initialize(input)
    @input = input
  end

  def inspect
    "<Event status=#{status} note=#{note} velocity=#{velocity}>"
  end

  def status
    data[0]
  end

  def note
    data[1]
  end

  def velocity
    data[2]
  end

  def button
    Button.new(note)
  end

  private

  def data
    @input[:data]
  end
end

class Button
  YELLOW = 62
  RED_LOW = 13
  RED_HIGH = 15
  AMBER_LOW = 29
  AMBER_HIGH = 63
  GREEN_LOW = 28
  GREEN_HIGH = 60

  def self.map
    @map ||= {}
  end

  def initialize(note, output = OUTPUT)
    @color = 0
    @note = note
    @output = output
  end

  def on(color=GREEN_HIGH)
    Button.map[@note] = color
    @output.puts(0x90, @note, color)
  end

  def on?
    Button.map[@note]
  end

  def off
    Button.map.delete(@note)
    @output.puts(0x80, @note, 100)
  end

  def off?
    not on?
  end

  def toggle
    color = colors.at colors.index(Button.map[@note]) + 1
    if color
      on(color)
    else
      off
    end
  end

  def colors
    [nil, RED_HIGH, AMBER_HIGH, GREEN_HIGH]
  end
end

@input = UniMIDI::Input.gets
@input.open do |input|
  $stdout.puts "send some MIDI to your input now..."
  loop do
    m = input.gets
    m.each do |m|
      event = Event.new(m)
      $stdout.puts event.inspect

      if event.velocity > 0
        event.button.toggle
      end
    end
  end
end