How does Kira dye the string in Gathering Blue, and what does she use to dye them?

All the dyes were natural based on the vegetation grown there. Our ancestors used the same process. Certain plants like onions produce a yellow color when they are boiled. The string would be dipped in the boiled water. To turn it to the desired shade, the amount of time it was left in darkened the shade. Indigo was the plant used to achieve the color blue. The book lists some of the plants Annabella raises and will teach Kira how to use. Ex. madder and bedstraw-red; tansy, greenwood-yellow;yarrow-yellow and gold; hollyhocks-mauve;broom sedge-yellow and brown; St John's wort-brown; chamomile-green; woad-blue. These are all real plants but not all grow in the same area.