As IKEA describes, "Belgium is a gray" and to brighten up the city, the 'Choose Color' campaign was set up, literally infusing the city with bold, bright colors.
The campaign involved setting up a series of vibrantly-hued billboards that from afar, just seemed like big paint chips. From a distance, the only elements that were visible on the billboard were a big splash of color, the IKEA logo and a price tag, that seemed to be floating in the middle of the ad for no reason. But upon getting closer to the ads, people would soon see a very faint blueprint-like outline for one of IKEA's products.
Since it seems fairly odd for a poster to be essentially advertising the color green for $24.99, the ads incite curiosity and encourage people to look at them a little more closely.