This is a simple iPhone pixel test; black, white, red, green, and blue screens. Verify that each color is solid, unbroken, and with no stuck pixels. Scroll down to see each color.

Your screen should be white. Check for stuck dark pixels.
Your screen should be black. Check for stuck light pixels.
Your screen should be red. Check for stuck blue or green pixels.
Your screen should be green. Check for stuck red or blue pixels.
Your screen should be blue. Check for stuck red or green pixels.