For the colour scheme, I always thought that if you painted an aircraft 2 colours then the eye can pick that up as 2 objects. Thus missing one part of the aircraft. I like the big yellow Sea Kings. All one colour and easy(ish) to see against the ground, but not so much against the air. The best (in my opinion) method of conspicuity is to keep moving. Take positive steps to make yourself visible. If someone spots you and thinks 'what the f*** is he doing?' means that you have been spotted. This involves manouvering, lights, radio calls and everything. Don't assume people can see you, make them see you.
Not a lot of help if you're hovering, winching etc. But then life was never meant to be easy.