TIP:
If you’re going to do use a gradient for color B, I recommend getting one that is made for matching socks, i.e. you get two 50g skeins that change colors at the same rate (ideally dyed from the same blank). In order for me to have both a gradient iris and gradient brioche, I had to break up my cake into 5 parts to account for all the gradual color changes, resulting in a slightly less smooth gradient on the iris.