Murray was slightly more dapper in a black tuxedo than at the earlier press conference when he wore an eccentric green checked jacket with clashing checked shirt, but still managed to display some of his individuality with a brightly patterned bow tie as he joked around on the red carpet.
Blonde-haired Swinton, who plays a social worker in the film, dazzled in a floor-length soft pink gown.
The red carpet experience may have been a bizarre one for newcomers Kara Hayward and Jared Gilman who make their first appearances on the silver screen in Moonrise Kingdom.
Fans were also in raptures just before the cast’s arrival as the Cannes jury, headed by Italian director and actor Nanni Moretti, took their turn to walk the coveted red carpet.
Ewan McGregor, who is part of the nine-strong panel, was cheered as he stood at the top of the steps at the entrance to the Palais des Festivals and gave them a wave.
Other jury members Andrea Arnold, who directed Wuthering Heights, and actress Diane Kruger were also out in their finery this evening.
Alec Baldwin, who is supporting new film Rise of the Guardians, Tim Roth, who is heading a jury charged with picking out emerging talent, and Desperate Housewives actress Eva Longoria, also attended the official opening ceremony.