Glory be to God (line 1)
The poem begins with an expression of Christian humility in the face of "God's Grandeur" (to quote the title of another of Hopkins's poem). The first line lets us know that the poem will be a "hymn to creation," inspired by the Biblical Psalms.
For skies of couple-colour as a brinded cow (line 2)
After the first line, "Pied Beauty" turns into a nature poem – a major departure from the Psalms in the Bible. Although much of Christian scripture does praise nature, it does not do so in such a specific and sensuous way.
Whatever is fickle, freckled (who knows how?) (line 8)
The speaker does not try to explain the way the world is, he just admires it. The parenthetical "who knows how?" discourages us from questioning God's designs.