Unless grey is a mix of black and white it's going to lean towards a colour such as green, blue, purple, etc. Adding any colour bedding to a room painted in a green-grey is not going to change the look of the wall. Only repainting will do that. However, I think the fact that it has greenish undertones makes it more on trend since greys are developing into more natural versions at the higher end of home fashion. Based on what I've seen at European Design shows in the past year, colours like toast, biscuit, and driftwood are coming in very strongly. Why not embrace the natural look of your green and transition into beige and white, accenting with pops of brighter colours? If this doesn't appeal to you and you're firmly in the grey camp, then I suggest you repaint. Ask at the paint store for someone to point you to the true greys and paint a sample to see what you think of it.
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