Setup:

Main monitor: 4K scaled at 150%
Second monitor: regular scaled at 100%

Steps:

1) Open Unity and place it on your regular monitor
2) Click on a ColorField to open the Color window and place it on your 4K monitor
3) Click on the ColorPicker and move your cursor in the Scene view

Expected result: there's no offset
Actual result: major offset (you can see this in the preview of the ColorPicker)

Repro on 001562e0d12e

Similar to case 1016307, which is fixed in branch editor/tech/windows-dpi-colorpicker. However, this case (case 1018591) only adresses the issue when the Editor and the Color window are on separate monitors