Question about blue dye tests...

How accurate do you think the blue dyes might be? Can I see others true positive blue dye tests

I took a blue dye test yesterday, had a vvvvfl, came up after 3min. I took another this morning, another vvvvfl showed up within 3min. I know blue dye tests are evil but these were thick and blue, just really light. (And the only ones the store had)

When I normally buy the blue dye and think I have a vvvvfl, the next one I take always shows negative but these two both look positive.