Agree with carrieandjimh, You will need to connect the two colors through prints on pillows, curtains, rug etc. Can you post a pic of the sofa and wall color so we can see what we're talking about here? Thx.

Wish i found this Q &A before. So many beautiful people advising and sharing here! I am Repainting Tropical Queenslander with dark red and orangy timber floors and this thread is so helpful. I painted Whisper white and it is throwing so much Green it makes me so sad I am going to repaint. I get loads of tropical sun in the north facing - with eastern morning sunlight. Was just about to go and buy Natural White just to cover it. Do you think it will be too dull/warm a colour. I do like a fresh feel and contrasting with vivid white decorative trims. The whisper white looks nice For a while in the morning while the morning sunlight throws read up onto it but then it returns to a green

I agree but my comment means that my opinion is that colour and the way to find out would be as you say in person at a paint store but I reiterate that I have a very trained eye for colour and can only go by the sample above the rest is up to the home owner.

As a former art restorer and now retired I am proficient at mixing colours, I agree with the two above me taking the pillow case is a good idea and the other thing is to do is make sure that the grey has a blue touch as some have a green touch or a brown touch etc so it is possible to get the wrong mauve grey which has a red/brown base to the black and white to achieve the mauve/grey, overall the paint store have people who will help you pick the right colour as often a colour on a small sample looks a lot different when applied to a whole wall. Good luck