To reproduce:
1. Open a new Unity project
2. Maximize editor window with the green arrows in the top left
3. Exit fullscreen mode with the green arrows

Expected result: top editor bar stays the original color
Actual result: top editor bar becomes pink

Reproduced on:
2019.3.0a2

Not reproduced on:
2019.2.0b1 2019.3.0a1

Notes:
- Only managed to reproduce on 2019.3.0a2
- MacOS 10.14 and 10.14.4
- Also reproduces on OpenGLCore but it immediately goes back to original color after exiting fullscreen mode