Beautiful! I think the obvious choice would be the yellow for most people, however the floorboards and cream walls would feel like too much yellow and make the rug just a dark blob in contrast. Consider the intricacies of the teal, blue and mustard in the rug. I would suggest a fabric sofa in the teal shade, and layer lots of tactile throws and pillows in the other mentioned colours. Keep the yellow in the rug, the accent that picks up all the yellow in your existing space, the small flecks in it will highlight against your flooring in particular.

Do you have any photos? Might be easier to offer advice! I love dark floating floorboards too! These articles might help you choose the right sofa! https://www.houzz.com.au/magazine/forever-furniture-a-buyers-guide-to-the-sofa-stsetivw-vs~49223903 https://www.houzz.com.au/magazine/buyers-guide-need-a-new-sofa-stsetivw-vs~27011754 https://www.houzz.com.au/magazine/how-to-pick-the-best-sofa-for-your-living-room-stsetivw-vs~44137925

I think you are on the right track with a tan colour... Will mix great with the greys. I'm a huge fan of a lovely aged leather. A black/dark grey pattern rug could add some interest and texture to the space as seen in below images. If you go a tan then consider the colour of your tv unit & coffee table to be different as to not look too matchy and another colour for these other than the same as sofa.

Hello, I would recommend these sofas from our current collection. They would all be good neutrals that don’t fight the darker carpet, and can be styled up by cushions. Also, we can scotchguard for you to make sure they don’t stain! We also have a 10% discount for our Houzz customers at the moment- use the code CQ4W1D4140.