Flowers that grow in the west are colored by the sun setting so they turn bright red. That's why red flowers that grow in the west are used to make red dye. They're the closest to the actual color of the red sun, so they're prized by painters and other artists for their perfect color for dye.
As you're smashing the flowers into red dye, a little girl comes up to you and points at the paste. She says, "赤ね (あかね)?" (That's red, right?) You look down at the red dye on your fingers and nod. She's right, it is red.