If you want a warm color, it will contrast, not match.

I have slate blue and cream colored furniture. I’m thinking of adding a caramel colored leather chair to the room. It won’t match the slate blue but instead will contrast with it while blending well with the cream furniture.

I was thinking of adding caramel too. The sofas are grey not cream, do you think it will still contrast and blend well with grey?

Your photos are very dark, so it is difficult to see the colors, etc. Plus computers and various devices can also display colors differently.

I lightened one of your pics.

The sofas are appearing as more of a cream color on my screen, also. But you say they are grey - and now I do see a bit of a grey cast.

Your room looks fine. Very nice, in fact.

If you want to bring in caramel, etc., of course you can. Those tones - and various warm tones, in general - work well with greys. So don’t be afraid to mix greys with warm tones.

I'd go with a complementary color like orange. Here are a few living spaces with gray and orange for inspiration:

San Francisco Chic Victorian · More Info

Pinewood Circle · More Info

Our Work · More Info

These are more photos to show the actual sofa color. (These photos have a different rug tho, I moved this one under the breakfast table and put a slate blue wool one on top of the jute rug instead).
I got these sofas thinking they are neutral, and I know they are, but they don’t go with everything as expected. They are a light slate grey color, not the typical neutral grey. It depends on the lighting, sometimes I see a green hue in them, sometimes I see a greige one. So they are really tricky.