Here is a list of things to check if your screen is displaying strange colors or lines:

1. Check the connections and power cords from your monitor or TV, and make sure they are securely plugged in.
2. If your monitor or TV has an on/off switch, make sure it is turned on.
3. If your monitor or TV has a power indicator, make sure that the indicator is lit.
4. Press the menu adjustment buttons on the monitor or TV itself, and adjust the menu settings to make sure that the screen display is set correctly.
5. If the display issue only occurs on a particular input (VGA or HDMI, for example), check to make sure the video source is connected correctly.