Sometimes colors "speak" to me and I immediately know which ones to use. And sometimes this is far from the case. I'd originally chosen colors that looked good together "on paper", but clashed when knitted together. I was pretty sure of myself every time and almost started knitting straight away, without making any samples. In the end, I'm glad I took the time to test them out, and it's proof once again that making samples can save many hours of work!