Seeing red can make patients do just that, according to new security advice being issued to hospitals by the government.

An official booklet, Effective Management of Security in Accident and Emergency, gives, among other things, tips on decor, warning that certain colours can raise temperatures while others have a soothing effect on patients. Colours to avoid are red and bright yellow, which can be a source of irritation. But green, bluish green and yellowish green can calm difficult patients.