Be careful when using those when it's a vvvfl because it's hard to tell if it's an evap or if it's an actual color line. Go for the red dye because it is a little easier to tell the difference. Blue dye is cheaper but if you live in the US, at Walmart they have .88 cent red dye tests. I've had no issues with those. So basically if you're gonna use blue dye, hold off until you're at least 12 dpo so you don't get your hopes up. In March on every blue dye I used, evap line.