Why are we so taken with blue?
As Robert Frost notes here, all the blue hues we are taken with - blue in birds, in butterflies, in gem- stones, flowers, eyes, even sky - are just reminders, 'appetisers' if you will, for the blue we all truly desire - the blue 'so far above us', the celestial kind.
(If you want to read more about our fascination with blue, read here: 'Why So Blue?')
Fragmentary Blue - Robert Frost
Why make so much of fragmentary blue
In here and there a bird, or butterfly,
Or flower, or wearing-stone, or open eye,
When heaven presents in sheets the solid hue?
Since earth is earth, perhaps, not heaven (as yet) -
Though some savants make earth include the sky;
And blue so far above us comes so high,
It only gives our wish for blue a whet.