No, not a good idea... trying to blind people walking there? And paying electricity provider for light source?
What, if a passerby is a welder, carrying with him his dark glasses, so, he still would be capable of discovering your dish?
OK, let's stop imagining unreal scenarios...
The easiest way of camouflaging a dish is to cover it with a box or a diaphragm, which would be transparent to Ku-band waves (frequencies),
but opaque to visible light. The box could have a label with words like "Rain monitoring sensor" or "Pollution monitor", or... whatever your
imagination and probability suggests...
The very idea of concealing of a dish is a good one, though...