Roses are Red...
Most people are familiar with the couplet that you find on many Valentine's Day cards.
Roses are red, violets are blue
Roses are red, and my love is true
(Alternative second line):
Sugar is sweet, and so are you
We will buy very pretty things
A-walking through the faubourgs.
Violets are blue, roses are red,
Violets are blue, I love my loves.
A poet as well as an author, Hugo wrote the songs that appear in his novels. There is no reason not to believe that all the words are his own creation, although authors do on occasion borrow lines from elsewhere and adapt them to their own use.
It is possible this happened here, and Hugo may have borrowed from Edmund Spenser's The Faerie Queene, Book Three, Canto 6, Stanza 6:
But wondrously they were begot, and bred
Through influence of th'heauens fruitfull ray,
As it in antique bookes is mentioned.
It was vpon a Sommers shynie day,
When Titan faire his beames did display,
In a fresh fountaine, farre from all mens vew,
She bath'd her brest, the boyling heat t'allay;
She bath'd with roses red, and violets blew,
And all the sweetest flowres, that in the forrest grew.
Spenser wrote The Faerie Queene, based on the Arthurian legends, a few centuries before Hugo (1590). While there is a long distance between Spenser's words and the Valentine's Day cliché, it is quite possible that Hugo was the bridge. It is equally possible that Hugo wasn't basing his verse on Spenser at all.
Some might wonder how the words found their way into English from Hugo's French. There is a possible explanation. Les Misérables was published in 1860 in both French and English. During the American Civil War (1860-1865), it was standard issue to all Confederate soldiers. They are said to have called themselves 'Lee's Miserables', making reference to their leader General Robert E Lee2.