Test pictures are not visible

[Schraube11]

At the tuning menu there is the possibility to activate different test pictures. But I do not see them when I want to tune something. The LEDs are lit in the corresponding color, but the menu occupies the entire screen. If I then confirm the save with the green button, I briefly see the complete picture, until the Enigmalight main menu appears again. How can I see the test images to adjust the colors correctly?