The Reason Behind What You See
The beautiful flower parts you have been studying have a purpose! Flowering plants are specialized to produce seeds.
The end of the stigma is the same "Y" shape in this mature seed pod. It has grown larger as the seeds inside grow. It started out yellow. Why would it turn green?

A mature seed pod is actually the stigma, style and ovary. What is inside? Seeds!

Growing tulips from seeds takes a long time, so new tulip plants are usually produced (propagated) from little bulbs that grow off an older bulb in the ground.