MacBook – 2017 MBP screen flashes green or yellow when waking from sleep

Macs will wake up in response to many hardware events. Changing a USB/Firewire/Thunderbolt cable or even plugging in / powering on a connected device will wake Macs that are sleeping. Keyboard presses, clamshell sensor detecting an open of the display lid will also wake up a sleeping Mac. These are pretty well known and obvious, even if you don't realize a pet or power fluctuation can cause a wake event.

Two software items will also wake a sleeping mac and both rely on the power management / system management controller. Both are seen in the Energy Saver preference pane. This is how applications can do the same thing as hardware and wake your mac.

For macs with a battery - the power adapter needs to be connected and powered for much of this to work. The Wake for network access is both the standard WakeOnLan (WOL) as well as Apple's Bonjour Sleep Proxy. I like the article About Wake on Demand that explains how Apple has extended the concept of WOL and made a service.

If you disable these two items - software can no longer wake your sleeping mac and you can know if it's a hardware event or a software event. The other answers go into how to look at the logs to know which event has made a specific wake up request. Hopefully this helps frame the bigger picture of how your mac can take a cat nap with one eye open.

Although it's likely a hardware issue, you could try a few things if you don't want to get hardware help from Apple yet.

1. See if this happens when booting in Safe Mode.
2. Install a clean OS on an external drive to be sure it's not some extension or conflict.
3. Look in the console logs - see if you can see any obvious errors.
4. Try with other monitors and cables - it could be a bad cable or display. An EFI or firmware update might be needed to make the mac handle this situation better (it should never freeze) - and a report to Apple with details how to reproduce this might help get a fix sooner unless others have reported this specific combination.
5. If you have alternate RAM - do try swapping that in for testing. The newest macs use RAM heavily for display buffering - and wake from sleep is a time when you first can see issues with RAM going bad.

I'm lucky to have stores close by and would head there for a diagnostic checkup - so keep that in mind - it could just be a hardware failure / bad RAM, but anything you can do to narrow down the cause or rule out software / accessories by disconnecting everything but the bare minimum could save you a trip to the shop.