When the formula for the techelet dye was lost, some adopted a custom of adding a blue stripe to the tallit itself. Others opted to add a black stripe of mourning for the loss of techelet. The black stripe gained popularity in Europe of the 15th through 19th centuries, when black-and-white clothing was more common among Jews in general.
The blue stripe is now seeing a revival in the 20th and 21st centuries, but it’s actually the older of the two customs.
Sephardic Jews believe the debate over what color is appropriate precludes wearing colored stripes, so they wear white stripes on their talleisim.
The Gemara asks whether the tzitzits should be the same color as the tallit itself. Because the Rambam holds that they should, Baladi Yemenite Jews, who resisted the influx of Syrian customs, adhering instead to the Rambam, did not wear a tallis of any particular color. One occasionally comes across older, more traditional, Yemenite man wearing a rich blue or red tallis with matching strings, with or without stripes.