Nothing is impossible.
Casara has loved the blue rose all her life and even has a tattoo of one on her ankle.
See, roses come in all colors. Each color has a corresponding meaning. Red for love. Yellow for friendship. Purple for passion. Since blue is the only color rose that cannot exist in nature, blue is considered the impossible one. Moreover, having a blue rose means attaining the impossible.
Literature around the blue rose goes back pretty far. One of the best old stories about the blue rose is this one:
The blue rose is a symbol of hope in yourself — the belief that you can achieve the impossible. This folktale gives such a realistic and simplistic example of using the symbol for good — using the symbol to circumvent obstacles that would normally be impossible to beat.