What paint colours would go with this?

[4EverScottish]

Our lounge is north/south facing and has a small window at the end of the room which we're planning to replace with folding doors. At the moment it's magnolia, we've yet to redecorate since moving in. The hearth is beige stone, we're not replacing that, the fire is black and the mantlepiece is cream.
We've got a beige, grey and red rug which we want to keep as it matches the curtains from our old house which will fit when we have the new doors. Our old house was a rental with lilac walls so we're happy not to reproduce that colour scheme! However, we do want a bit of bright colour.

What colour would you choose for the walls? We've looked at paint charts and can't agree - I was thinking red for at least one wall, but magnolia (no way!) and grey have also been suggested. We've got a brown leather sofa (sorry!) and beige cushions with red flowers.

We're doing it ourselves so we're limited to paint as none of us are good at putting up wallpaper.