The promise of rain! The dark blue of the heavenlies, light blue the Holy Spirit. Pearls; Jesus as the pearl of great price as we as believers 'shine like stars': crystal. (Phil 2:15). Pearls, crystal and sodalite.
Joel 2:23 (NKJV)
Be glad then, you children of Zion,
And rejoice in the Lord your God;
For He has given you the [a]former rain faithfully,
And He will cause the rain to come down for you—
The former rain,
And the latter rain in the first month.