He has clear/natural/maybe silver coloured main with a brown cross. I believe he used to use full bed of ALU, so he may be trying a gut/poly hybrid. The brown cross looks closer in colour to the new Babolat RPM Power than it does Element. Hard to say really, the images on Getty aren't the best because of indoor stadium + flash.
Gael Monfils of France in action against Dominic Thiem of Australia during men's singles match within 2020 Australian Open at Melbourne Park in Melbourne, Australia on January 27, 2020. Thiem won the...
France's Gael Monfils reacts as he plays against Austria's Dominic Thiem during their men's singles match on day eight of the Australian Open tennis tournament in Melbourne on January 27, 2020. /...
It was a complete guess with no basis but it does look like it. I just wonder if he would choose Element as a cross. Maybe he was scrambling for a cross and someone suggested it due to his sponsorship with Luxilon.
I am sure someone here will find out soon enough and post the actual string he is using.