A MUST to have the same color if you want it to show nicely on the back of the towl!!
Interessant question, I do not understand why the colour of the thread of the bobbin must be the same that the top thread, the colour of the bobbin thread can be seen only on the back side ???
Does the thread of bobbin must be the same or only the same colour?
emblibrary has a video on embossed designs. They use a med wt cutaway and the same color thread or a contrasting color thread