If you can get a swatch of that fabric I would! Periwinkle is a hard color to match, sometimes it looks more on the blue side and sometimes it looks more on the purple side. If you can get Americolors I would really go with those. You might try mixing the royal with violet or regal and if you need to go darker maybe a touch of black. But if you can get a hold of that material that will really help you out.Good Luck!