Why is my brand new screen changing colours

@brendenmcc35391 try this. Dial (*#0*#) [without the brackets] ➡ Samsung Hardware Diagnostic Test Menu. Here you can check your R, G and B responds for your display. Let us know what it tells you. Ultimately it does sound more like a hardware issues then software based on "at a darker brightness it eventually goes back to normal". That would lead me to believe that this is a voltage issue going to the display. I would try another screen (from a different Vendor) and see how that performs. If that does not work properly, then the issue will be with the main board. Schematics are partially available and to work on your main board, you require some special tools good skills and experience. It might be easier to just keep the brightness of the screen down to a manageable level.