Blue dye vs red dye

Chelsey • 27, Happily Married, Baby Boy born 12.13.18 👶🏻💙

This is an honest question and is not meant to be offensive...

Nearly every single post I see with a blue dye test faint line, there's comments saying try again tomorrow with red dye because the others are faulty and known to give false positives. So WHYYYY does anyone bother with the other? Clear blue costs the same exact amount as First Response at the stores near me, so I really just don't understand.