When I was writing the series, one of the features which I enjoyed developing the most was the Protectors' hair. I think there's just something incredibly cool about unusual hair colours and it also helps to mark the Protectors out, making them stand out in their extraordinary world. It took me a while to decide if I wanted the Protectors' hair to be streaked with colour, or to completely change though and even now, when I see a picture of someone with completely blue hair, I wonder if I've made the right decision! Recently, it has also become fairly fashionable; the trend was even featured in the Sunday Times: http://www.thesundaytimes.co.uk/sto/style/fashion/Beauty/article1194493.ece
I've used Pinterest to collect a few of my favourite pictures of colourful hair, to give you an idea of what I envision the Protectors looking like - and perhaps to inspire you to try it out for yourself. The school where I work is getting everyone to dress up as a book character for comic relief and I'm currently trying to decide whether to be a Shadowhunter, or buy some hair chalk and go as a Protector...
Arcan Hair - I couldn't find pictures of hair with silver streaks in it, but I did find some very cool pics of entirely silver hair
Also,because I couldn't resist...