The rainbow/colored pattern is moiré. It happens because the camera sensor’s pixel grid and color filter interact with the monitor’s RGB pixel grid, creating aliasing patterns. The overall shape distortion is likely a mix of your phone’s wide-angle lens distortion and the camera not being perfectly parallel to the screen.

To avoid it completely, the best solution is not to photograph the screen at all—take a screenshot on the computer instead.

If you must use a camera, you may be able to reduce moiré by slightly defocusing and then resizing the image smaller afterward, but this usually isn’t very practical with a phone camera. Keeping the camera square to the screen can help reduce perspective distortion, though it won’t fully eliminate moiré.