When you call QColorDialog::getColor with QColorDialog::DontUseNativeDialog, and the initial colour set to a colour in the "Basic colors", the dialog will open with the colour set to the colour in the grid with the opposite x and y position.
For example, when the initial colour is set to rgb(170, 0, 0) located at <1, 0>, it will come up as rgb(0, 0, 127) located at <0, 1> in the grid. Then when you open it again with the new initial colour the opposite happens.