Wyrd42

As somebody on the autism spectrum, enough so that my parents took me to a psychologist when I was little, who diagnosed me as "bright but very quiet", or in today's parlance, Aspergers, I can see a lot of potential autism-like traits on a number of characters, but the only one I'd feel certain in my judgement on is Susan.  Susan is definitely autistic.  High functioning, yes, but she's definitely on that spectrum. 
Noah and Grace are both part alien, as I understand Noah's character, at least.  Their social issues can be adequately explained by what we know of their childhood, though, so a diagnosis is not feasible.  
Tedd has his/her issues, but autism doesn't seem one of them to me.  There are some traits that could be autism, but s/he seems less likely to be diagnosable than Noah and Grace.

We have the diamond's remains evaporating, a single crate very near Ellen appears to be the only crate that was open prior to the golem and wand emerging, and text from that golem showing that the wave of magic that awoke it, the wand, and the bird mostly flowed into Ellen. That the color has no connection to a mysteriously colored gem that is called a diamond despite being green seems to be stretching things a bit too much.  I'm all for watching what is actually said  in the comic and for checking your assumptions, but there is a limit to how much we can avoid speculation. I could easily be wrong, but that's why I say "almost". My opinion on the color's source is based as much on knowing Dan's writing styles as what is literally said in the strip, but the amount of emphasis he's given on the DD's colors and on Ellen's new hair color, despite the massively added complexity of color based hints in a greyscale comic seems to be either an exploding barrel of red herrings or to actually be connected.
 

The green certainly comes from the dewitchery "diamond". There is a really good chance that the magic was drawn to her because it created her. While I don't care about her hair color(other than curiosity at where Dan is taking that), but I hope the changes to her form aren't permanent. Her breasts are so large and her waist so small that she looks deformed.  I like fv5 on males as it enhances the sense of change, and is often used to lampoon the male social identity's more ridiculous aspects, though I'd really like to see more variety in the transformations and less of a focus on large breasts, but supersizing the already enhanced traits and doing so so often really takes away from the quality of the comic, in my opinion.