This proverb is about the color of the sky foreshadowing the weather...
A red sky at night
Is the shepherd's delight.
A red sky in the morning
Is the shepherd's warning.
People thought if the sky was red at night the next morning would be fair weather. But if the sky was red in the morning, it would be rainy and windy by nighttime.
There's a similar proverb from 1831 Weather Lore:
Sky red in the morning
Is a sailor's sure warning;
Sky red at night
Is the sailor's delight.
There is a similar proverb in France about when the sky is red (click the link to read it). There is also a similar Occitan proverb about the red sky (click the link to read that one).
The rhyme at the top of the page can be found in The Little Mother Goose (1912), illustrated by Jessie Willcox Smith.