B737 Overhead panel switches
 

Hi guys/gals,

Does anyone know why some switches on the overhead panel on the 737 have a red socket/background while others do not. For example, the Yaw Damper switch socket is red while the window heat switch sockets are not. Is there any logic behind this? Also, I understand the white panels (fuel, electrical, hydraulic, air con&press) relate to things affected if a fire switch is pulled. Are there any other useful or fun to-know points regarding the 737 cockpit design that you know of?

Of course the "+" on the panels. Push on it when the panel is not lighted.