Left: Ellsworth Kelly, Yellow over Dark Blue, 1964-5
Right: Mark Rothko, Yellow, Blue and Orange, 1955
Ellsworth Kelly met Rothko at a party in MoMA in 1961. Postwar American painters are not my field of specialty but I think that it may be suggested that Kelly is making an overt reference to Rothko in this work.
Interesting comparison— lovely blues and yellows in both works!
This made my day