painting dining and living room with a quite dark olive green paint
It's up to you, Probie. In my neck of the woods, the dark colors are all the rage. If you wanted to break it up a little, you could do an accent wall in a lighter color. If it's a really dark room to begin with, (no natural light, etc.) maybe a lighter color on the walls would brighten it up a bit. It's your house, do what pleases YOU!