Is there any particular reason why Psylocke has her hair dyed purple? Don't get me wrong, purple is awesome I'm just wondering why she has her hair that particular colour?

Oh I see, she still looks great with purple hair either way!

...one thing that irked me a bit in the Sisterhood story (well...everything irked me) was that the Brit bod had been lying in a coffin for however many years and in death, our bodies' hair and nails continue to grow....so we shoulda seen at least a few inches of mousy blonde roots come through, not that Fraction or the colorist gave a hoot about the tiny details.

Actually, when we're dead our hair and nails don't continue to grow, our skin just dries and recedes making it appear as if they had grown. Also, even though she is in Kwannon's body her hair is still purple. Just as when she had dyed her blonde hair purple, it turned out to be lavender or light purple. Now that she has naturally dark hair, putting purple dye over it turns it into a dark purple which appears black in dim lighting. I have purple hair, believe me, I'm the closest thing to a purple hair expert you're going to find. This picture from Uncanny X-Force clearly shows her still purple hair. Her X-Force minimate also has purple hair.