I would suggest different colors than black and blue. I found myself not able to differentiate unless I tilted my laptop monitor away. I can't imagine that color blind users would have a better time. May I suggest red and black?
However, I'm really confused. I am color blind (red-green) so I always try to make the life of other color blind people (and myself) easier. I hate red and black. When I was young and in school, I find that most people think the contrast between red and black is great, so teachers use red ink to mark our homework, and other students use red ink to mark important parts of their notes. It is very, very difficult for me to tell which line is red and which line is black.
In the article I was inspired by ( https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/findl... ), the author used red and black. I have to try really hard to see which edges are marked. So I don't want to give other color blind people like me a hard time in my game.
I do understand that there are other more rare color blind types (e.g. blue) and I would like to make my game accessible to all users. My experience is that most non-color-blind people also find the contrast between blue and black is enough. I used blue ink instead of red ink to mark important things in school, and teachers and other students can differentiate them easily.
No offense, but may I kindly remind you to check your monitor setup and whether you are color blind? Perhaps there are something wrong with your monitor screen and you are not aware of it?