What does "bleen" mean?

Of an object, blue when first observed before a specified time or green when first observed after that time.

Bleen

/bliːn/ adj

adj ·Rare ·Advanced level

Adjective

1
Of an object, blue when first observed before a specified time or green when first observed after that time. not-comparable

Blend of blue + green; coined by American philosopher Nelson Goodman in 1955 to illustrate concepts in the philosophy of science