How do I add color to this space with paint?

Light to medium sage/greens, warm beiges, soft yellows, to contrast with dark woodwork. Ceilings could be painted light blue, if desired. Bulkhead below loft egde could be painted a more intense color as a focal point, if you like. Room with Christmas tree could be painted in a brighter shade of orange, red, etc., to energize that room, if desired. Although coral is the 2019 color, it doesn't work for everyone.

What colors are your upholstered pieces?

Are floors bare pine or oak? How much light enters during the daytime?

Check out Better Homes and Garden's website, or Behr, Sherwin Williams, etc. for sites where you can upload photos of your rooms to try colors before purchasing paints.

Pull in colors from a favorite piece of furniture, window treatment or something you really like. I'd keep ceilings white so the color doesn't overwhelm the space. A pretty pastel yellow is my favorite, or a soothing sagey green for the walls. You could use a color from the tiles above your cabinets if you don't like my yellow or green...lol

Hardly any light during the day, we have chocolate colored sofa, loveseat, and recliners. Planning on hardwood floors!

The first question I always ask myself before I paint anything part of my home is, "What Am I trying to achieve?" If its more light, I naturally will look for paints with semi gloss finish that can throw extra light around. If I am looking for color, I like to use colors that naturally compliment the metals and wood work in an existing space. If you have dark wood colors, you might want to try lighter colors like Celadon or Sage, I personally am not a fan of yellow or gold, I feel that color has been over done. Its like every house with a lot of wood work I see had yellow for the walls and other colors will work just as well. Warm whites, soft greens, taupe, and light warm grey can also work in cabins. :D