Blue dye vs pink dye?

Question

About two hours ago I got a faint line on a blue dye test.(🤗) I just took a cheapo pink dye test from the dollar store and no line showed. 
Could it be my pee wasn't concetrated enough?

Answer

I don't like the blue dye tests, I hear so many stories about false positives because of evap lines that look like positives just because of the color.

Answer

Could be. I don't the ones from the dollar store. I took 2 and they were negative, 2-3 days later took a more expensive one and got a positive.