You mean the hands in the pockets?
There is of course a perfectly rational explanation.
You see prior to attending the event Joachim took a nap on the couch. And being a perfect gentleman Joachim can only nap in one position, lying on his back, with straight legs and his hands folded on his belly.
That's where mademoiselle Athena comes in. Inspired by her kusine (female cousin) Josephine, she decided to apply green nail-polish on her dad's fingernails. In the middle of the process Joachim woke up, but as a doting father it's of course impossible for him to admonish his daughter.
And since miss Athena expressed delight with the result of her work, Joachim of course could not remove the nail polish. As a perfect gentleman Joachim will consider any wish from any lady, even a mischievous daughter, a command. And as Athene believed dad should wear green nails on the job, that's what he did...
In the car he didn't have time to remove the green polish anyway, so Joachim opted to bend the rules a bit and park his hands in his pockets.
Had people spotted the green nails, they would have looked disapprovingly at him.
- A perfectly attired gentleman does not wear shades of nail-polish that conflicts with his shirt!
- It's true, I have it from sources...
Thanks, Iceflower