How would i make a circuit that? Answered

First, you would need a body suit covered in photo resistors. Then, each resistor would have to be attached to a micro controller, several in fact. Those micro controllers would have to be in turn connected to another microprocessor to interpret the data being received. That processor would have to output the net result of the data to an LCD display which would tell you... how much light was hitting your body. Useful, but not what you want.

To tell you how visible you are, I.E. how well camouflaged you are, there is no sensor or device that you could integrate into a suit to tell you how camouflaged you were.

In short, I believe the technology for an indicator of camouflage is still many years away. Camouflage is an art form that strives to make oneself blend in to their surroundings, and there isn't a scale of hidden-ness to judge oneself on. It all depends on the quality of the pattern and the scrutiny one is under.

I hate to burst your bubble, but It is a sharp pin to avoid.