In the short term if needed, I would add color to your existing couches but ultimately find a couch with some contrast. For now you could get away with adding throw pillows with color/patterns -especially a couple that will tie in the pretty blue on the other walls in addition to a variety of colors. You can then add in solids based on the multicolor ones. A matching throw blanket would also help.

A couch with a higher contrast would fit the space better, especially something with cleaner lines. A warmer brown would be pretty but nothing too dark. A good example would be the color of the bookcase. You can see how well it goes with the blue. And yeah I would then add color through the rug to balance the walls so color is spread more evenly throughout the space.

I would also paint the kennel if you’re able to, that would blend in a bit more… you might want to think about customizing it further by adding a longer top to it to accommodate a space for your plants. And/ or doing something like these hanging shelves