Wow, this is an interesting question... it took a bit of thinking!
I always feel like I've been attracted to Asian guys forever, but after thinking, it's been quite a recent development! however, this is only because where I'm from (Ottawa), there aren't very many Asian people at all. We had a few in my high school and none in my elementary school, so I didn't really start getting interested until I came to Japan 5 years back on exchange.

I remember there being this guy, Take, in the homeroom next to mine and he was tall, quiet and played the violin and I thought he was the sexiest thing ever. <3 sadly, I was way too shy to say anything so nothing ever happened, but I guess he was the first, and I would have been 17 at the time!