An electronic device with a display displays a user interface on the display. The device determines a first set of content-display values for one or more content-display properties of first content that corresponds to a respective region of the display. The device determines a first set of control-appearance values for one or more control-appearance parameters based on the first set of content-display values. The device displays a control in the respective region of the display, where an appearance of the control is determined based on the first content and the first set of control-appearance values, and displaying the control includes applying a blur operation to the first content to generate first blurred content and overlaying a translucent colored layer over the first blurred content.