wiring back up camera

I have 04 chevy avalanche and want to install vr-3 back up camera. The manual says to conect the camera to reverse light. This would mean the camera would only come on in reverse . I would like to be able to manual turn on and off camera . I know i could connect it to a toggel switch . But that would mean runing wires all the way to the fron and drilling into dash. I would like to use the switch on dash that turns on the light in bed of truck. There is only one bulb and i real dont use this light all that much . When i conected the red wire from camera to red wire just before bulb and the black wire to ground . the camera comes on . But when i turn the light off the camera still stays on. There are to wires going to bulb red and blue . When i test wire red with meter i get power . When i test blue wire when light is off i get power. I know it not like olden days when power was simple . Dont understand this . Can some help me figure this out . Is it possible what i am trying to do . Dop i need a relay or something that will make this work { remember this kind of stuff when hooking up trailer lights. need a separate box ) . Please tell as much as posible of what i need ( name or model no. ) and how to install.

Took truck all apart and wife screaming she needs truck

Thanks  From a Newby

Your cargo light always has power going to it.  The switch grounds it.    Your reverse light is always grounded, when you put the vehicle in reverse it supplies power to the light and the camera.    If you want to use that switch to power the camera you will have to use a relay.

Turn the light on and check voltage on the 2 wires again.  Now only one of them will have 12Volts on it. To wire the relay you need to apply power to terminals 86 and 30.  85 needs to be connected to the wire that did not have 12 Volts on it.  Terminal 87 goes to power of your camera.

does the relay need to to go by the switch or can it go just before the bulb

some one say i can get 12v from trailer plug .would that help . what is the relay called and where would i get one

trying not to run wires allthe way to front if possible

thanks