Blue pens and black pens

this is probably a really random post but I had to get some reassurance, I finished 6 papers and for about half of them i used a blue pen because my black pen finished halfway through one of them and I just never got another black pen, I know the instructions say dark blue or black and that's why I used it, but I've seen a few things about people being told not to use blue pens and I'm freaking out a little, has anyone used blue pen and not had issues after you got your results? Im just worried that my answers won't show up on my scans and idk 💀 I know this may seem stupid but this has genuinely been freaking me out now and I need to know if its just a thing in certain places where they've been told not to use blue pens at all