Kurenai no usuhanazakura niowazu wa mina shirakumo to mite ya sugimashi - Shika Wakashu(English Translation & Meaning)

紅の薄花桜匂はずは
みな白雲と見てや過ぎまし

Roma-ji: Kurenai no usuhanazakura niowazu wa mina shirakumo to mite ya sugimashi
English Translation: Had the crimson
of the pale-blossomed cherry
not glowed so softly,
would I have taken all for white clouds
and simply passed them by?
Meaning: If the faint crimson of the pale-blossomed cherry had not glowed, would I have taken it all for white clouds and simply passed it by?
Commentary: Book One Spring Poems 18

Among cherries one might mistake for white clouds on the hills, it was the faint tinge of crimson in the pale-blossomed cherry that let the poet know they were flowers. The delicate eye that notices the slight difference between white and crimson is the poem's charm.
The author is said to be the mother of Prince Yasusuke. With the next poem by Fujiwara no Morozane and the reply to it, three poems form an exchange.

The first line, "crimson," gives the color of the "pale-blossomed cherry" of the second line.
The second line, "the pale-blossomed cherry," names a cherry with faintly crimson flowers; the same word appears in the fourth line of the next poem and is the heart of the exchange.
In the third line, "niou" means a color glowing beautifully; "zu wa" sets up the hypothesis if it had not.
The fourth line, "all for white clouds," draws on the traditional likening of mountain cherries to white clouds, taken up by "white clouds" in the first line of the next poem.
The last line, "would I have passed them by," closes a kakari-musubi with "ya" and the counterfactual "mashi," imagining that the poet might have gone on past.
Source: Shika Wakashu
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