The King has praised David Hockney's "galoshes" and revealed he cannot wait for the artist's next project as the pair met at a Buckingham Palace lunch.
The event to celebrate leading figures from the world of politics, science and the arts was hosted by the King, after a service at the Chapel Royal.
Members of the prestigious Order of Merit - including an array of pioneers from broadcaster Sir David Attenborough to world wide web inventor Sir Tim Berners-Lee - watched on as six new members were formally appointed.
As the King hosted a pre-lunch drinks reception he complemented Hockney on his yellow Crocs, worn with a flamboyant suit.
The artist who used a wheelchair insisted on standing when he met the King and Charles looked down at his feet and said with a smile.
"Those yellow galoshes...beautifully chosen."
Hockney is set to launch an immersive experience which will give visitors the opportunity to engage with audio and visual elements to follow a journey through his art.
The show, created by the 85-year-old Bradford-born artist, will launch early next year at Lightroom, a new four-storey venue in King's Cross, London.
Charles turned to renowned architect Lord Foster and said, "I can't wait to see what he does next".
Also appointed to the order is geneticist and cell biologist Sir Paul Nurse, awarded the Nobel Prize for Physiology and Medicine and now chief executive of the Francis Crick Institute.
Television presenter and author Baroness Floella Benjamin was among the six new Order of Merit members chosen by the late Queen in early September and appointed by the King earlier this month.
She spoke with pride about being the first woman with her heritage to be appointed to the Order: "I just feel absolutely thrilled to know that one of Her late Majesty's final wishes was to have such a diverse list, and to be the first black woman from the Caribbean to be included in the Order."
Baroness Benjamin said the Queen's decision would send a message to future generations, "Come, if Floella can do it, you can do it."
The Trinidad-born peer first came to prominence as a presenter on the popular BBC children's programme Play School.
She has gone on to write more than 30 books with her memoir Coming To England now studied in schools, she served as Chancellor of the University of Exeter for 10 years and as Chair of the Windrush Commemoration Committee, helped organise the National Windrush Monument unveiled at Waterloo Station.
In 2010 she entered the House of Lords, where she speaks on diversity, equality, and children's issues.
The Order of Merit was created in 1902 by Edward VII to honour leaders in the arts, sciences, culture and military and appointments are in the Sovereign's personal gift.
Members are limited to 24 individuals and 22 were able to attend the lunch including ex-prime minister of Australia John Howard and playwright Sir Thomas Stoppard.
Sir David Attenborough said of the Order of Merit: "It is a mysterious thing but it works. It is a great honour because it is such a variety of people from such a cross section of society.
"Membership of this group isn't selected by wealth, nor is it selected by aristocracy."
