Tap on the colors at the top of the screen to select them. Tap on squares to color them. You can color over a square with a different color. It will tell you the current selected color at the bottom of the screen. Press s to save. Press i to import. Press the back arrow to undo. Press the forward arrow to redo. Press the box thing under the undo to turn on and off the grid.
I got the grid part of the background from google. Save and share your pictures here: https://scratch.mit.edu/discuss/topic/484369/?page=1#post-4883724
