Screen artefacts - colored band with vertical stripes on MacBook Pro (15-inch, Mid 2012)

As a work-around, you could connect an external display and get a good picture again. That Mac would support a display up to 2560 by 1600 using its ThunderBolt-2/Mini-DisplayPort output. Conversion to [Full size]-DisplayPort is a cheap 'just wires' adapter.

Because you can see that the data are intact inside the computer (as shown by your 'good' screenshot, the problem is either in the rasterizer/screen-generator hardware, display cables, or the display itself.

Since part of the screen is fine and part is really 'not fine' that strongly suggests a problem in the display module itself.

Your appointment at an Apple-owned store for an in person evaluation is free, in warranty or out. Apple repairs displays by replacing them. You are likely facing a bill in excess of US$500, but the folks at the Genius Bar can provide a FIRM (no surprises) quote.

Parts from Apple for a 2012 model may be scare to non-existent. There may be nothing the Apple store can do for you.

Third party fixers collect old wounded MacBook Pros, and can swap the (used) screen from a Mac that drank a glass of water into your Mac with (presumably good) chassis.

The real decision is whether and how much you are willing to spend on this old Mac. Consumer Reports Magazine, when talking about Appliances, suggests that when the cost to repair exceeds HALF the cost of a new one, you should buy new. Computers are going obsolete FAR faster than washing machines.

You are facing some sort of internal failure.

Get expert service and support at the Genius Bar.

Click ▶︎ Start a Service Request. ⚛️

Need more help?

• Chat now or call 1-800-APLCARE.
• International Support.

Click ▶︎ Check Repair Status. 🔧