|Pictured: not my foot|
So I went over to my friend's house the other day to do some movie watching. Some of our other friends were also due to come over, so we sat outside and waited for them. While we were out there, my friend had the good idea to bring out food substances to sustain us. Her food substance of choice? Watermelon.
Now I'm not a particular fan of watermelon, but I am a fan of spitting, so we engaged in a seed-spitting contest. One of the things I do like about watermelon (besides the seeds) is the colour. The red-pink is just so cheery.
Physics time: why does red look like that? Actually, we're not sure about that. We can explain why things appear red, though.
Visible light has three colors: red, green, and blue. These are different from the primary colors we learn in elementary school. The colors we use to make the other colors in fingerpainting are red, yellow, and blue. That's because using pigments like paint to make colors is a subtractive way to make colors, and the red/yellow/blue combo is pretty similar to the magenta/yellow/cyan (and black) scheme used in printing, but I digress.
White light is comprised of "all" colors, which can be made from red, green, and blue. The watermelon (remember that?) appears red(ish) because the RGB light from the sun hits it, but the green and blue wavelengths are absorbed, and only the red is reflected to our eyes. The rind appears green because red and blue are absorbed, leaving only the green to reflect. Only blue is absorbed by the yellow part of the rind, yellow being the marriage of red and green. Finally, the black seeds appear such because all red, green, and blue wavelengths are being absorbed, so there's nothing to reflect back to your eyes.
It's like spitting little bundles of negative light. (Not really.)