Don't know about Yves Klein specifically but remember seeing this video from Vox:
"Why these all-white paintings are in museums and mine aren't" [1]
"Why these all-white paintings are in museums and mine aren't" [1]
One woman was conducting the tour for three people, when they stopped at one of these all-white paintings.
She was describing the potential meaning behind the work, and noted that sometimes the artist expresses textures, or covers some background work.
It's hard to describe, but I felt this sort of absurdist joy when I watched all four of them lean in very closely for half a minute, only to discover absolutely nothing unique about the work in its texture or color.
Maybe sometimes art isn't made for the observer, but the observer's observer.