Click picture for detail.
They have complex lives.
Sometimes I think I liked them better when they were just white dots and they all looked the same.
(Sometimes I think that about people too.)
Other times I marvel. And I do like a good marvel.
Here's the current extent of my understanding:
It starts at the bottom-left and follows the wiggly path. If it goes right, it's getting redder; if it goes left, it's getting bluer; if it goes up, it's getting brighter. When it gets to the top it goes boom.
From star evolution lectures.