Spades!! said "Lighting is critical. But what I’m talking about is most staff at paint stores are not trained to give advice on colour. I once asked about the different undertones between a couple of colours and the lady looked at me like I was crazy. Undertone is critical to picking the right colour along with the lighting in the room. Any interior designer will take that into consideration. It is a hit and miss with the staff at paint shops. "
Keep in mind that training for that is not easy. That is often something you either have, or you do not. With years of experience, you can pick it up. To the level of a designer, probably not. Used to run a paint store, and to get someone who could do both the physical, sales, color matching AND consulting is difficult at what paint stores pay (over minimum for sure). Designers specialize, and get paid more. Definite case of getting what you pay for.