Hashem created all to reveal His glory to us. The ultimate realization of God will be in the World to Come, where the soul will thereby derive endless pleasure, yet even in this world Hashem is revealed to us somewhat. The glorious heavens speak of the glory of their Creator.
The sun shining by day, benefiting indiscriminately all flora and fauna paints the sky with God’s kindness. So too, the soft glowing moon at night, accompanied by hosts of endless stars, softening the effect of the dark night, paint the other half of the sky. The endless space and countless stars sing of the honor of the Creator.
Kabbalistically, the colors each carry a different meaning. Blue is the color of תוכלמ, majesty.
Hashem’s throne of glory is blue. The sky is meant to remind us of God, Who is always there, above us. In truth He is everywhere, but we perceive Him as being above us as in the sense of his ruling over us and being beyond us. Perhaps this explains the choice of wording "םירפסמ", which has the same root as the word "ריפס", blue sapphire, the material of Hashem’s throne. This is the glory the endless, lofty, blue sky tells us of.
Another interpretation of "עיקרה דיגמ וידי השעמו" is that the constellations, situated in the heavens, tell of Hashem’s doings with His world, through the language of astrology. Furthermore, the clouds, or lack thereof, tell of His desire to soon bestow us with life-giving rain.