It's perfectly fine! No need to stress
Sometimes orchids and other plants will get a little purple blushing like this in different places, sometimes it's due to higher light (think of it as a suntan or a healthy glow) and sometimes it's just due to genetics. Either way it's perfectly fine!
As far as being under watered, it doesn't really look too shriveled or anything, so that's good.
I will say this though, if it has been in significantly lower light than what you have planned for it, raise the light levels gradually, so you don't burn it!