There has been past discussion about the difference between the U. sandersonii "typical" and "blue flower" forms. Here are flowers of both that have been grown side by side under exactly the same soil, light, temperature, water, etc. Note that the typical has much more narrow ears and less frilly skirt. The blue flower has a slightly darker blue color than the typical. The typical has larger leaves and flowers easily and profusely, while the blue flower has smaller leaves and flowers occasionly.
blue flower (bottom)