QColorDialog - wrong RGB values returned from native dialog when color picker tool is used

The QColor returned from QColorDialog when native dialog's color picker tool is used contains wrong RGB values. The returned values seem random: they are 0-30 points off (up or down), but on the other hand the same color returns always the same wrong value. This happens with both: static QColorDialog::getColor() dialog and with created QColorDialog.

If the color is chosen using other tools e.g. RGB Sliders the values are correct. Except if also the picker tool is used (e.g. pick the color and adjust using sliders), then the result is wrong too.

The attached example can be used to reproduce the problem. Click "Pick Color", choose the slider view in the color dialog and 'RGB Sliders' from the combobox (just to see the RGB values). Now, use the color picker tool to pick the brownish color (160,100,100) in the main window. Notice the correct RGB values in the color dialog and press OK. The received color looks wrong and the numbers are off: (141, 79, 81) on one computer, (152, 75, 80) on another.

Tested only on macOS (Sierra and High Sierra). EDIT: Now tested also on Windows 10. This seems to be macOS specific problem.