2 months of propagating! Why are some basil plants pale while others are green?

Hi! I’ve been on an herb propagation journey (basil/mint/rosemary) and I LOVE it. It’s an endless source of joy and satisfaction every time a new plant “kicks off.”

Now that the basil plants are growing in full force, I’ve noticed some have pale / yellowish leaves while others are deep green. Any idea why that might be?

Open to any and all other tips / feedback, as I’m still a relative newbie!