In this context, bleen means "blue if observed before a time t, and green if observed after," whereas grue is the other way around.
It is also a color, seen in the muddy rainbow of a puddle of motor oil after the rain, colored niobium body jewlery, and around extrmely bright light sources. It describes when all or most perceivable colors appear visibly and at least somewhat distinctly in one place, and implies a shiney, metallic, glowing, neon, reflective or incandescant sheen.
It is also a halliciongen which may be absorbed through the skin. Finally, it is a fictional animal. Bleens are sightless, land dwelling invertebrates, so named for their call, which sounds rather like "Bleen." The color of bleen comes from their opalescant, shifting, multi-hued bodies. They are unusual among invertibrates in that they are large, warm-blooded, and do not need to be kept wet, possessing a soft, non-posionous skin that is generally dry to the touch. They are approximately equal to humans in avarage mass, but undefineable in length or height as they are somewhat shapeshifting and ameoba-like.
Today on the Discovery channel - the mating rituals of the Bleen!
2) (Verb) Hold your finger behind someone's head so as to poke them when they lean backward.
2) Phil: Ouch! You poked me in the back of the head!
Clyde: Ha! I bleened you!