Gather all your supplies. I would suggest buying knock off scotch tape because it tends to be less tacky than the brand name tape.
Add a base coat to your nail. I use a strengthening base coat because my nails break easily.
Paint both your hands with a coat of red. I had to use two coats because the one I have is thin.
Cut off a strip of tape and place diagonally on your nail. Make sure the polish is completely dry. I suggest placing the tape somewhere on your arm. The oils in your skin will make it less tacky.
Paint the entire nail that's uncovered with blue. The tape should create the straight edge for the color division. You can peel off the tape once you finish painting the blue.
If the red wasn't completely dry, go ahead and fix patches the tape may have created.
Draw a white line between the red and blue. It'll cover up the jagged edges that might have appeared when trying to touch up the patches earlier.
Cover with a clear coat of nail polish to protect the white and blue from chipping too quickly. Afterwards, take a cotton swab and clean up the edges with nail polish remover.