Some venues have a rule stating 'bivvies only, no tents'.
Depending on where you're fishing it my help to blend in with the background, but if the venue doesn't prohibit tents or specific colours, why not. If others on a public venue get the hump, surely that's their problem, not yours.
If they really get upset about it, next time take along a disco ball and start that up in your tent at midnight and make it look like a rave!