Hizzoner’s no blond bombshell.

Mayor Bill de Blasio Tuesday denied he’d lightened his salt-and-pepper hairdo, a day after his staff tweeted a photo that appeared to show him with gold locks

“I don’t know how the photographer involved, Rob Bennett, managed to make my hair look lighter, but my hair has not changed between yesterday and today,” de Blasio laughed.

Bennett, a former news lensman who’s worked for The Wall Street Journal, is de Blasio’s chief photographer. The photo in question shows the mayor in a Team USA jersey to support the World Cup. He blamed the lighting.

“I want a full investigation,” de Blasio joked. The hairdo question, asked during an unrelated schools event, followed a query about an Iraqi militant’s terrorist threat against the city.