When I work with silk, I use an acid dye which gives beautiful color and can only be used on silk.
The second step is to discharge color using a nature themed stamp. The discharged areas are overdyed and then stamped with a textile paint using the same shape as the discharged one. It's a 4 step process - what you're seeing is only the first step, and my favorite part - the dyeing. I love seeing white silk turn into such vibrant colors.
I usually do 3 colors on a scarf or sometimes 2 if the 2 colors melt into a pretty third color.
I work with several kinds of silk including China, charmeuse, crepe du Chine, chiffon and a blended scarf of wool and silk. Each take the color a little differently which makes the process more fun. For example, because China silk is so thin, there is a lot of wicking of color giving all kinds of lines and interesting movement. It's fun to see the dye move throughout the fibers.