The red dye is a “sour acid dye”. I haven´t tried this technique, but the colors turned out absolutely beautiful, so it´s on my list of things-to-try.
The yellow dye is reactive dye.
I made a sample-set, sewing together 7 different types of natural fabrics. And putting each sample-row in each of the dye-baths. The blues are indigo. The creams are the natural dyes, unprepared. The yellows are the reactive dye. And the pinks are the sour-acid dye. The fabric qualities from right to left are:
linen, silk organza, silk jersey, silk brocade, bamboo, viscose, 77%viscose & 23% nylon, cupro (copper-viscose), cotton and wool. All 100% unless otherwise defined.