Since a couple of years red plastic cups are now being sold in stores in The Netherlands alongside the more common plain white cups. Not because the Solo company started selling them here, but (ostensibly) because a red cup carries the connotation of college students partying and alcoholic drinks, and apparently that image sells cups.

The colour of these cups is a cultural import from the US; if your frame of reference is the cup's portrayal in media, then the red Solo cup appears to be exclusively used for partying and drinking with abandon (e.g., consider the image of college students playing beer pong), so you get red cups if you're a teenager organizing a party.