RUN IN TURBO MODE (shift + click the green flag) All of these effects are actually created with one line of code. One. Each mode consists of one equation with outputs the color code to use based on the x and y positions. mode 5 = combination of 3 & 4
Something I found about Scratch with this is that Scratch handles Sprite coordinates very interestingly. It uses the exact same function for both Fast Mode and Normal yet there is a difference in color, which is determined by the coordinates of the sprite. This can be mostly seen in the rainbow.