If you've ever wished for a real-world version of Photoshop's eyedropper tool, you're not alone. Korean designer Jinsu Park has created this "Color Picker Pen" concept, coupling an optical scanner with an RGB ink cartridge that can mix up any hue you zap.
Grabbing a particular shade of red, then, such as in the apple above, would be as straightforward as holding the optical sensor end of the Color Picker Pen to the fruit and pressing the single control button. Park envisages a slim display on the side of the pen showing which color has been picked up; the three tiny ink cartridges inside then mix together the right shade of ink for you to draw or write with.
Obviously this is all just a concept at the moment, but it's one that could be feasible. Optical color scanners exist, and printers work on the same ink-mixing principles; problem is, we're unlikely to see such a compact device anytime soon.