Quote from Arkarian:
I actually never thought that was an issue. I always thought of them as security doors-- orange ones lead to areas that require higher security than rooms with blue doors would.
Good, cause if color doors was an issue to you, maybe the Metroid series isn't for you :P
On topic.. I noticed that once you press a button on a X-Ray panel, the remaining symbols are scrambled but the buttons you used cannot be pressed again. I have an hypothesis that, while you don't have X-Ray, if you can press the same button twice in a row, it means that you'll never be able to get the code right. (ie.: the panel is in a different "state" than it is when you have X-Ray on) That's just a thought I had, from a programming standpoint... but I don't have a save without X-Ray to test this out.