Are Blue Dyes Reliable⁉️

*posted in another group as well*

AF came to visit for one day but she was super light (in comparison to usual which is heavy, painful bleeding for about 4 days). I spotted the next 2 days but only when I wiped. Never needed a tampon or panty liner. I’ve been taking all kinds of test and getting VVFL within the timeframe. The only test that is not working for me is the FRER. I think I may have gotten one faint line from them. Tomorrow will be a week away from expected AF.

My question is if taken correctly can blue dye test be reliable?