Would differences in say, hair colour and/or height be counted as deviance in this setting? Or is the definition looser than that?
Oh, oh! See, deviance in the eyes of the law and in the eyes of the society are a little different, and I actually included how they view hair color in this thing I wrote up about it. When it comes to hair, the only thing that's looked down upon and such is changing your hair color.
Changing your hair color isn't illegal, however, you'll be looked down upon for doing that, like looked down upon heavily. So, people generally won't do it. It's not illegal, per say, but people generally view it as tacky, tasteless, and downright weird. If you did it while you were underage and your parent(s) found out about it, you'd probably get beaten.
That's another thing, physical discipline isn't viewed as a bad thing in that world, but instead viewed as something that every child goes through. It isn't the law to spank your child (here's another thing with deviance), but it's seen as odd if you don't hit your child a couple of times.
But, back to the original point. If you have blonde hair and someone else has black, it won't really make a different. Now, if you're born an albino, that's a different story.