Race workers in yellow volunteer jackets and police in yellow safety vests were running past me.

NPR: Reporter Shares Account Of Bomb Blasts At Marathon

The yellow safety flags came out after a collision between Red Bull's Sebastian Vettel and Robert Kubica in his BMW Sauber.

BBC: Toyota accept Trulli time penalty

Dr Herxheimer, aided by Charles Medawar, from Social Audit Ltd, which has campaigned on antidepressant safety, examined more than 1, 000 yellow card reports about Seroxat.

BBC: NEWS | Health | Drug alert scheme 'deeply flawed'