The existence of lilac, lavender or purple rose seems like impossibility. Mentioning them is like telling a fairytale where a prince was asked to acquire a rare thing for a princess, as if they are some precious unattainable entity but they do exist in real life. Just as the color suggests, they symbolize enchantment and magic. Sending them to someone is conveying that the recipient is rare, unique and one of their kind. It is the symbol of love at first sight. It symbolizes romance which is expected to be magical, precious and bewitching.