Adjust the slider to set the speed (actually the angle by which the sprite turns clockwise each screen refresh). Click the buttons to change costumes. I thought I'd try to make a Newton disc (see links below), which didn't quite work. But the motion blur is quite nice nonetheless. Why doesn't the Newton disc work? Well, the biggest problem is that Scratch has a screen refresh rate of 30 fps (frames per second), which is too slow to fool the eye. We perceive it as flashing colors rather than a single color. That's why I tried to cheat a bit with the artificial motion blur, but the blur isn't enough. You could increase the blur until it "works", but then it would look that way even if it was completely still, which is not what I was going for here.
Inspired by @ffred's comment on my Color Spinner project: https://scratch.mit.edu/projects/438213783/#comments-162806929 The color wheel costume is from this Wikipedia article: https://en.wikipedia.org/wiki/Newton_disc
