Reproduce steps:
1. Create new project
2. Open Unity>Preferences and make sure OS X Color Picker is disabled.
3. Open System Preferences>Accessibility and increase the Cursor size to at least half-way along the slider
4. Select a "Main Camera" in Unity's Hierarchy
5. Click on the "Background" color field in Inspector
6. In Color picker window select Color Eyedropper tool
7. Move the mouse around the screen
8. Notice that cursor is being displayed in zoomed pixel area

Expected Behaviour: The color picker's zoomed pixel area shows what is under the cursor, but doesn't show the cursor itself.

Actual Results: The zoomed pixel area shows the cursor, which sometimes results in the picked color being black or white and not the one under the cursor.

Did not reproduce on Windows, macOS with non-retina display.
Reproduced on macOS with Retina display.
Reproduced on versions: Unity 5.5.4f1, 5.6.0b11, 5.6.1p4, 2017.1.0b9, 2017.2.0a4