Lower level is in construction phase

Lighting plays an important role too. Please add a photo of your lower level even if its in construction so we can see the space better.

Purchase a sofa cover in the color of your choice.

Taupe goes with everything ....gray white blue navy ....it's a neutral like your walls.

You can make your sofa fun with some crazy pillows or some damask pillows or furry or silk....just depends on the overall feeling you are going with downstairs,

I am not totally sure what you are asking so I could be off with my input. It would be nice to see the taupe color tone of the couch. Some Taupe's are grey and some are more pinkish....

If it is a lower level why do you feel you need to carry the gray walls to this level, too? You could bring the gray and navy in with accessories.

Your whole house doesn't have to be matchy matchy. But, the rooms should speak to each other. If you have gray and white upstairs as the main colours, I would carry the white into the lower level. White and taupe look great together. I'm not a fan of a single accent colour, it's kind of a dated look. How about shades of blue upstairs, not just navy. And a different accent colour downstairs plus a blue. That way you would have lots of white and a bit of blue on each level.