I used painters tape to tape off some stripes and they used red paint to cover all the white or if you're a three year old cover the entire thing red!
After that dried, we peeled off the tape, added star stickers to the top left corner and painted it blue.
They also wanted to add some heart stickers.
After the blue dried, we peeled off the star stickers and added their hand print (which didn't show up very well).
Proudly showing me their flag!