Question about FRER

I shined a light on the back of the test and saw a line. Now, I did that with an older test that was in the trash and there was no line. I can't tell if there's color though. I also took a blue dye (I know they're bad) and it looks like I have a faint positive on it. I'm not getting too excited. Just curious if anyone has had the second line with a light shined to the back of the test and it ended up being a BFP.