A new show of Johns’ work opens up next month in Chicago. It focuses on the importance of gray in his work, and includes 141 works from 1955 to the present.
There’s a nice article about it here.
From the article:

“I think viewers of this exhibition will be able to experience the great potential and meaning that gray has for Jasper Johns,” said James Rondeau, Frances and Thomas Dittmer Chair of Contemporary Art at the Art Institute of Chicago and co-curator of the exhibition. “Gray is much more than a colour to him. It is an analytical tool, a measure of distance and separation, and a means of getting to the heart of his practice as an artist. Through such a close exploration of a subtle and restricted range, Johns is able to make abundant and commodious discoveries….”