OK, help you Poetry buffs, please?

I once read a poem, probably written in the 19th or early 20th century. It is a dramatic poem, and I have heard it recited with a musical background.

Roughly, one of the lines is something like 'the moon is white instead of yellow' or visa versa. It made so much sense to me in the mental state I was in at the time.

Can anyone remember that poem?

Many Blessings

Gwen