Use TURBO mode to see the demonstration pattern. (Press the <Shift> key and click the Green Flag for TURBO mode). The "1 Line Challenge" is to produce an interesting pattern using only ONE line of code to calculate the color of each pixel. If you'd like to enter, see the original project by @Scratch-Minion.
I made colors! I have no real idea why this looks like it does. I understood exactly what I was doing up until the last couple of steps, where I made it awesome. Too awesome for me to keep track of, it would seem. :P Credit for the original project goes to @Scratch-Minion.