We have had a light grey wall-to-wall carpet upstairs for ages now (well over 20 years) and it really needs replacing. We have had a couple of goes at looking for something different, but even light beiges, and honey-colours don't seem to be as versatile for mixing with different colours for the different rooms.
I would go with grey again, but I found a little notebook kept by DS1 when at primary school, in which he had written "Least favourite colour: light grey"!
However, as for the original question - as others have said, a grey floor and grey lounge suite is the perfect basis for a lovely selection of bright or pastel colours - cushions, curtains, vases, pictures, pouffes can all be in contrasting colours to pep it up.
Our Welfare State. Is it broken?