At a perennial sale once I found an unmarked canna with green leaves, and when I asked what color the flowers were, they said they didn't know. After looking at the leaves for a while, they decided it was probably yellow. Later that summer, I found they were right. How can I find that out for myself?
Orange colored cannas invariably have orange or yellow streaks on the leaves. Yellow cannas don't have orange streaked leaves. The almost white canna's streaks or similar variations in foliage will be very pale.