Simple answer: Greys, whites and very light browns
More long winded answer:
Couple of things:
1/ Start a mood board/pinterest board. Pin ideas and colours that you like. Don't think too much about it, just what you like.
2/ Aim to have a background colour for a room/area, then the colour of your biggest furniture (e.g. sofa, cupboards etc), and one accent colour. I would recommend that your main colour is light and neutral. Off-white or grey is good. I would avoid magnolia. Your accent colour is your choice!! it can be bold or subtle, but it should be sparse around the room. You can use this colour for your lamp shades, soft furnishings or picture frames etc. (Brass is very in at the moment)
3/ Furniture colours: Do you already own the sofa and furniture? if yes, you may have to think about what colour they are now and what will go well with them (post some pics). Most people buy/have furniture first, then decorate a room (it should ideally be the other way around, but not everyone has that luxury)
4/ Buy some lining paper, and paint it the colours you are considering for your walls. Don't paint the sample directly on the wall. Why? Because with lining paper, you can move it around the room and see how it looks on different walls, catching the different light. Also, place it where walls join (fold the sample so that it is on both walls). Place it behind your furniture to see how it looks. Check the colours in the day and at night. Stuff looks different in different light.
5/ Lighting is really important. if builders are involved, I would be thinking much more about where lights will be placed, rather than the colours (for now). Lights on the ceiling are usually not the best place. Consider having multiple light options for a room, e.g. wall lights, ceiling lights, spot lights, etc. so that you have options at night and during the day. Where will you have lamps? make sure sockets are there.
Hope this helps.