For most people it is easier to think about about a color in terms of hue, saturation and brightness than in terms of red, green and blue. Yellow is one hue, but is made of red and green, which might not be very intuitive.
In this episode we learn how we can read the hue, saturation and brighness of the pixels in our display. We then use that information to define a new color for each pixel.
Using this technique we can create programs that modify the colors of any image.