You'r absolutely right... Ryman's work is amazing. They had an exhibit in the Disney Gallery dedicated to him a few years back. It was so cool to see some of the original conceptual art for Disneyland.
The exhibit was very well put-together as well, telling the story of how Walt was planning to pay a visit to the financiers, but didn't have anything concrete to show them. Apparently, Herb put together one of the first concept pieces the weekend before Walt's trip.... and the rest is history. Without Ryman's work, Walt may not have gotten the financing that he needed, and we may never have had a Disneyland!
"I could never convince the financiers that Disneyland was feasible because dreams offer too little collateral"