Abstract: A device operator interface includes a first operational parameter display field for displaying a first adjustable parameter characterizing a first operational state of a device and displaying a first distinctive color associated with the first operational state of the device, a second operational parameter display field for displaying a second adjustable parameter characterizing a second operational state of the device and displaying a second distinctive color associated with the second operational state of the device, and a control element manually operable to change the first parameter in a first state, and manually operable to change the second parameter in a second state. A color display is associated with the control element, and the color display is configured to display the first color when the control element is in its first state and is configured to display the second color when the control element is in its second state.