Reverse lights not working

I have a 2003 gms somoma/chev s10...my reverse lights do not illuminate when put in reverse..not sure where to look for the switch that would activate these lights or if there is a fuse that is in this loop that I need to check. I have checked the bulbs and they are good. Any help would be apprieciated...also just want to say that is is a standard tran thanks again.

There should be a switch on the trans with a pink wire and grey wire. The pink wire is power to the switch from the B/U fuse in the underhood fuse block. The grey wire feeds power to the vehicle B/U fuse wich is also in the underhood fuse block. From that fuse the power is fed to the B/U bulbs via the green wire.

What is the best way for me to try and access this switch...through the cab or from undernieth? I will check the underhood fuse box in the mean time for any blwn fuses...are the lights on their own circut...because nothing else has appeared to be affected by the loss of power to them...knowing that may help me eliminate whether it is a fuse problem or simply a switch..