It's a dilemma because you know your stuck with it for years once it's on. We recently painted our cedar exterior. Started by agreeing on a general colour and then buying a series of sample pots. We finally decided on dulux colour bond dune. Amazing in itself as we rarely agree haa. It was a nice mix between beige and grey. We bought the 10 litre tin and went to work. After completing one wall I thought the paint was taking a while to dry as it wasn't getting as dark as the sample. My husband thought it was because of the lighting. I took a piece of wood and painted the sample which we loved and the paint from the 10 litre can together and yes they were a different shade. The hardware store had accidentally mixed the sample pot in double strength. It was all fixed up and we really love the result. So it was Dulux Colourbond Dune. I think it would be perfect with your roof colour.

I would have to agree with keeping the wall with the windows neutral. Either stick with all neutral and bring colour in with accessories and some natural wood would lift the room too... if you desire a feature wall, can you use the other wall in this shot? If so you could go bold with an inky blue for drama as below or a grey as these look great with the black sofa...

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.

Thanks for the photo's it really show's what should be painted with what, just by looking at the first photo looking towards the stairs, the painted bulk head would really bring the ceiling down and then again the second with the bulk head above the external door, wall colour is the right choice for me. cheers