Yes start at blue, considering Nunu can gank if needed with only blue buff. Also a better blue start is to kill the big wolf with consume then start blue to level off of blue and decrease jungle time.

Great guide, I play Nunu on TT (with a Trynd) and Nunu jungles like a boss, but I would argue that you don't need smite, as sometimes it pays to not have the enemy aware you are jungling and have them expecting you sitting there with a snowball in a bush for an early gank! (and having an exhaust later makes up for Nunu's lack of strong CC compared to stun/taunts)

Also Popping out of the jungle at level 3 with a blood boil on an ally and a Snowball + exhaust for the enemy is just brilliant.

After reading this guide I will have to try switch up my build order to rush negatron before catalyst and see how that works for me!