I have used Evaporust extensively on machine tool parts and some on gun parts. I love the stuff. But yes, it will remove blue, usually. I soaked a blued part in Evaporust overnight, all the rust was gone, the blue remained. I was too lazy to take it out and clean it up right then, so I left it in another day or two. Next check, the blue was gone. So, don't soak anything you don't want to get the blue off of.
but for rusted parts in general, the stuff is great! You can soak a steel part that is covered in scaly rust almost behond recognition. Leave it overnoght, or over the summer. The rust will be gone, the steel will be clean. Just rinse off the sooty coating and treat with something to prevent re-rust. Or don't - it leaves some sort of non-oily rust preventative of it's own.
Oh yeah, if your part has a high carbon content, it will leave it a deep black color, which I happen to like.
You can reuse the stuff indefinitely until it's too nasty to want to put anything in it, then toss it out in the backyard, no harm.
For blued parts, electrolytic derusting probably won't remove bluing. I have not tried it for that, so YMMV.