OK, so when Ian first appeared in this chapter in the back alley, his hair was definitely light brown. But his original hair is black. Then, a little bit later (still in the alley, btw), his hair got... darker? And it stayed the same dark brownish through the end of the chapter (except when he was in the shadows, because ya know, everything is darker in the shadows, so there his hair colour actually resembles the original).
Ahem. Maybe it's some sorta colouring stuff, not hairdye? Like... a cheap one that only works under the sun? Or rubs off after a short amount of time? IDK. Although I imagine a prince wouldn't just pop in to the corner shop and buy the cheapest hair colouring product available. So no idea how that happened.
Oh, and happy holidays! Thank you for the chapters <3