If I had a definitive answer for this question then I would invent a button that I could push to get the colours that work every time. Ha. I wish. Colour is way too tricky for that. Colour is a key element in human expression and therefore plays a big role in how we perceive, feel and respond to what we see. Every project has its own specific set of idiosyncrasies, requirements, intentions, technical limitations and opportunities and should get its own carefully considered solution that makes the most of colour. When deciding about colour we need to take many things into consideration, weigh them, balance them, analyze them and then make strategic decisions. Every colour decision should have reasoning behind it.