Young star clusters have bluer turn-off points than old clusters.

Question

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The turn-off point of a star cluster is the point on the Hertzsprung-Russell diagram where stars are leaving the main sequence and evolving into red giants. Young star clusters have bluer turn-off points because their stars are hotter and more massive, and thus, they burn their fuel faster, making them leave the main sequence sooner. In contrast, older star clusters have redder turn-off points because their stars have lower masses and are cooler, which causes them to burn their fuel more slowly, leading to a longer time spent on the main sequence.

Young Star Clusters Have Bluer Turn-Off Points Than Old Clusters