In Robert Heinlein's Future History, the song "The Green Hills of Earth" expresses spacemen's nostalgia for their home planet as they travel further into the Solar System. The reference to terrestrial green is doubly poignant because the song is, fictitiously, written and sung by a man who was blinded by radiation in space: Jetman Rhysling, the Blind Singer of the Spaceways, not exactly a new Homer or Milton but the herald of a new age nevertheless.
In a later future history, a different timeline and another planetary system, Dominic Flandry visits a planet where vegetation is mostly blue but where he nevertheless sees:
"...the unexpected and stingingly Homelike splashes of green." (1)
In the Future History, interplanetary economic oppression in "Logic of Empire" was followed by American religious dictatorship in "If This Goes On -." In Anderson's Technic History, interstellar economic oppression in "Lodestar" and Mirkheim was followed by social collapse in "The Star Plunderer," then by interstellar imperialism in several stories and novels. Thus, Anderson continued the Heinleinian tradition but in a longer series and on a vaster spatiotemporal scale.
Thereafter, Heinlein's lengthy novels, whether in or out of his Future History, degenerated into long, turgid conversational passages that are not to be recommended whereas Anderson blazed new trails in long speculative novels presenting new visions of possible futures. Thus, Anderson followed but surpassed Heinlein.
(1) Anderson, Poul, A Circus Of Hells, London, 1978, p. 85.