Screenshot doesn't have the correct colours

It's a photo taken by a phone camera. The window on the left is Shotwell, while the window on the right is a screenshot of Shotwell, taken with GNOME Shell on Wayland, being viewed in GNOME Photos. Notice how the colours of the icons in the sidebar and the pool table are different.

To prove that it's not a GNOME Photos rendering problem, here's the screenshot itself:

I have Intel Sandybridge graphics and:

[rishi@kolache ~]$ rpm -q mutter gnome-shell
mutter-3.26.2-2.fc27.x86_64
gnome-shell-3.26.2-4.fc27.x86_64