If I paint my room two colours, do you think they should be on opposite or adjacent walls?

Adjacent. Painting opposite walls the same colour, especially if the two colours really contrast can give a room a wierd elongated look.  more

You can really do it in any way that looks cool. Most people use different colors on each adjacent wall in a 4 wall room,so each color is opposite from each other. However if you have multiple walls, you can do a lot of crazy things with it that look good.  more

I would go adjacent, personally. I've done rooms both ways and that just seems to work out better.  more

Either can work or even split one wall into both colors or join them on a wall diagonally for a great modern feel.  more