I would say dark but they might show a lot of dirt what kind of floor is that ?

would be a shame to paint original hardwood flooring.

They are not hardwood. I would not paint hardwood floors. This is a soft-wood sub-flooring with lots of nail holes in it. I've painted this type of floor before. It works really well and it would be the best solution here. I'm just wondering about colours for wall and floor. I agree that dark shows dirt too much, but too pale would be too country. Need a more sophisticated colour.

Gray is hot you could do a brownish charcoal gray to compliment the wood and and lightest gray brown on walls.

What colors did you decide to paint your walls and floor? Pictures?

Instead of painting the floor, I'd give it a dark cherry stain.