I have heard that the stripes on a Tallit are either for Zecher Techelet or just a style/design. Firstly, which one is correct? Second, if in fact the stripes are Zecer Techelet, is there a problem of wearing Techelet on a Tallit that has stripes (Bal Tosif)? Would it be more appropriate to wear a Tallit without stripes or with white stripes when wearing Techelet or is there really no difference?
Lechatchilla the Minhag (Ashkenaz) is to wear a Tallit with black stripes. There's no problem putting Techelet on such a Tallit. Rabbi Dov Lior