Using this article for reference, sibling C and I dyed some of her cotton-and-nylon socks with liquid leftover from cooking spinach. Spinach produces yellows to greens, but doesn’t stick very well (isn’t “fast”). We added some iron (from an iron supplement) to make the color more green, and to hopefully make it darker and more fade-resistant.
The socks looked like something at first, but, like many naturally-dyed articles, quickly faded. Very sad 🙁 Sibling C is amassing a very pastel army of naturally-dyed socks. The one upside is that they coordinate very well.