Hi Davern,
Not sure where you are in the country, but if you can find a walnut tree, this fall put on some rubber gloves and pick up the hulls. I hear green is the best, but I never get those in time. I have used the black hulls with success. The squirrels will appreciate you cleaning off the nut for them. We have several walnut trees at work. I went out at lunch and picked up a big sack of hulls and piled the nuts on the sidewalk. The next day, all were gone. I have also used chestnut hulls. Thankfully someone else picked those up for me. Search on this forum for dyes, and you will find a lot of information. Good thing on the nut hulls is they have natural mordants, so the dyes set and do not rub off. Since you make your own (boiling all this outside is your best best bet), make quite a bit and you can do a dip for real even color.