Julie the Regular 4x6x4 cpfs (pre-washed are 14.5 x 21") have white stitching. However, other textile manufacturers also use 'white' as the cpf stitching has come to be 'standard' and is copied.
I went to measuring them for you this evening and the variation changes according to how old, how many times they had been washed, etc. . . but none were shorter than 20" in length or 14" in width.