It's blue because it's a model of the blue dracolich in the Neverwinter MMO. *puts on second pair of nerd glasses and pushed them up his nose* And as you can clearly see from the dragons bone structure and horn formation it was once a blue dragon hence why it's painted blue.
*Explodes in nerd...
I just thought I'd shard some of my nerdness... During the Extra Life session that WotC ran this year I donated a little and "won" a copy of Rise of Tiamat. When I opened my copy a handful of ToD stickers fell out and on the inside page was this... Woot!