What color carpet would match my sofa and walls?

I have a green sofa (a medium khaki/sage-ish green) and my walls are medium-light tan. I'm looking into buying new carpet and would like something medium/dark and non-brown. My current carpet is a light grayish blue and I absolutely hate it. It shows every bit of dirt and every spill ever made. I have a husband and two dogs and will hopefully be adding children soon, so I need something that will still look alright after some years. I'm leaning towards a rich, dark blue, but I'm really horrible with things like decorating. Does this sound like a good color combination to anyone? Does anyone have any suggestions?