Paint Samples

My kitchen is B O R I N G and I want to paint it. Our house is designed in such a way that is difficult to delineate spaces. Like a lot of homes nowadays there are a lot of open spaces and the living areas blend together. The kitchen and the dining room blend into the living room and is separated only by a short wall. So I am trying to paint the kitchen in the same color family as the living room, which is a subtle blue.  I would love to paint the kitchen a nice sage-like green. This is proving more difficult than I would like . I have three paint samples on the wall and they are definitely not even close to the green I want. I have three more colors of green I will put up soon. I would like to know why the color sample looks completely different in the jar or color card than it does on my walls! I understand lighting, shading, and all that crap but to have such a difference amazes me. I think I will post pics of the color I choose and the before and after of the kitchen. Wish me luck!