Blue rose

A blue rose is a variety of rose that does not appear in nature.

Mainstream Smurfs Media
In the cartoon show, Smurfette desired to see a blue rose so much that she asked Mother Nature, who then gave her a spell that she could cast before a white rose to turn it blue, with the promise that she would never cut the rose from its stem. However, as the spell had its effect of turning the white rose blue, it also turned Smurfette white and made her smell like a rose, attracting bees. In order to restore herself to normal, Smurfette was given another spell to recite before the blue rose which made it fall off its stem, pricking her finger with its thorn and causing both to change colors again.

Smurf Me Up! stories
In the Smurf Me Up! story series, Glovey Smurf was sent by the evil witch Baba Yaga to gather blue roses so that the witch can brew them into tea in order to become young again in exchange for the children she captured being set free.