I've gotten some comments on my BOB when the trunk of my car is open. Mine is a Camelbak in hunter's camo -- I would have preferred something less attention-getting in urban environments but it was on closeout.

Note that in addition to active signalling gear I have a large blaze orange bandanna in my BOB if I want to be more visible.

In urban environments I work hard to be discreet. Weapons and tools are concealed. My "stuck on a train" kit is kept in separate pockets from everything else in my laptop bag. Dark, muted colors are the rule. I'm glad to talk prepping with friends but I err on the side of caution with strangers. That means keeping things under wraps.