One of my favorite materials to dye with onion skins. Red and yellow will both work. Sometimes I use them together. I use a fair amount of onions when cooking and I generally save the skins in a ziplock bag. If I save anything wet (like the ends) I will put them in the freezer. Depending on the amount of fabric you are dyeing you may need to save up quite a bit of dye material.
*Pro Tip* When I’m grocery shopping and I notice that they are restocking the onions I will usually ask if I can have all the extra skins. They are always happy to give them to me and I end up walking away with a big ‘ol bag of skins! Score! Bonus tip: you can also ask the deli counter if they have any skins to give you. Just please be respectful of the people around you, don’t bother them at the lunch rush and don’t cut in line.
Stay tuned for a lesson on how to use onion skins to beautifully (and permanently) color your textiles.
**UPDATE** Today at the grocery store, I saw that they were restocking the red cabbage, one of my favorite dyes. When they do so they remove all the loose outer leaves. I asked if I could have them for my dyes but after conferring with a colleague, the person I asked said no, they don’t give that away. I was a little taken aback. I’ve never been denied before (though this is the first time I have asked about cabbage.) I have a cold and so I wasn’t in the mood to find out why or to ask if I could buy the trimmings. Has anyone else had a similar experience?