Off the top of my head, I’d guess it was symbolism of the “triune God” represented by three colossal Star Destroyers/one colossal asteroid. Coupled with an allusion to ancient Byzantium, used to symbolize Heaven the way it does in some of WB Yeats’ poetry; since Byzantum’s two major chariot teams bore the colors Green and Blue, with the Emperor usually bestowing favors on the Blues rather than the Greens. And related to other stuff in the Lucasfilm vaults that uses this symbolism, eg, perhaps some WILLOW sequels.
Other than that, I don’t really have any ideas.
What? No. It’s an error in the video transfer. Something wonky happened somewhere in the process of transferring the film to video and then producing the vhs copies. There’s no symbolism implied or intended. You often have very interesting ideas, but you also have a tendency to jump to way too many conclusions. There is absolutely ZERO evidence to support any kind of symbolism. The fact that the blue lasers only exist in a few shots of one particular home video release, where they are green in the vast majority of releases (including the actual theatrical 35mm prints I bet!) points to it being nothing more than an accidental flub.
Looks like someone didn’t get the joke.