Pick a color at the top of the screen, then hold down the mouse button to draw. The fuzzy at the upper right corner is highly interactive, it can change its pose or turn in a golden fuzzy, Mario or a flower pot. However, it does not affect the colors. Click it -- no johns! Select a brush at the bottom. The spray is not available, though. Click the eraser or Undodog to erase the painting. The arrow at the bottom is interactive. Click it!
Credit to Nintendo. The most powerful Mario Paint project ever! April 24, 2020 ~~ changed a sound; you now draw with the mouse.