Sorry for this being late Sim 613. Fortunatley i am aware of the halacha that permits the strings to be pretty much any color. Rambam goes on to say better to wear red strings on a red beged etc. first of all i beleive that color of stam strings can’t be the color of “techilis”. second of all the whole aisur of Bal Tosef is when one says that he is performing the Mitzvah of techilet and in fact is not. meaning when you find out what you were wearing was not techilet. you can’t just say oh well at least i was yotzeh mitzvas tzitis. no in fact your over Bal Tosef for saying you were yotzeh techilet.