Back a few years ago, new cultivars of Easter Lillies have entered the market. The climate I have is ideal for bulbs. I live in a Mediterranean climate, with temperatures above freezing, allowing the bulbs to grow throughout the winter.
The lilies were planted in the garden. From my experience with the white variety (the "old classic" Easter Lily), the bulbs are not affected by summer irrigation. Neither did the other colored varieties I have found. All the bulbs have survived in the garden for a few years. However, I have noticed that the shoots which emerged each winter were smaller and weaker than those from previous year. The old classic Easter lily, on the other hand, has remained vigorous and produced new pups. The colored varieties were too weak to survive and in their twilight they looked like low-growing grass...
So my guess is that the other colored varieties may have been different species or hybrids with different cultivation requirement. Maybe they needed a different climate? Colder? Warmer? They are often marketed as "Asian lilies", but I don't know if they are related to Easter lilies.