Stonewall: Poster Research

For our poster brief we are only to use 2 colours plus paper stock. A good example of this ( suggested by Simon) was how effective the Stonewall poster, 'Some people are gay. Get over it!' which only uses two colours and just typography. The iconic Stonewall's poster campaign delivers a short, to-the-point, zero tolerance statement to tackle homophobia across the UK. It is a very loud and eye-catching poster which emphasises the message it is portraying. 
I want this kind of short blunt message in my posters as I don't want anything to long-winded as it wouldn't be legible from afar. However, I would have to be very clear, precise and specific for it to actually work.