you could do that with an overhead projector, or if necessary with a beamer. you should take your time though ;). error correction will be difficult on the wall. best to sketch it out first with a pencil!
So what I can highly recommend to you is white mixed with a little bit of orange, I believe. You can buy this pre-mixed at our hardware store; it is a very light color like white, but you can see that it is not white. The advantage of this color is also that it is not as oppressive as many other colors, which can be very uncomfortable in the office.