Blue Mobline are found all over Hyrule, although they are must abundant in the Akkala region, specifically in the area just west of the Akkala Ancient Tech Lab. They are all over the Tumlea Heights and found on both sides of the Bloodleaf Lake. They appear elsewhere, usually in smaller numbers with other Moblins and Bokoblins. There are a trop of them on the Carok Bridge, that connects the Central and Ridgeland regions. They also appear in the Wasteland region, mostly found just north and northwest of the Wasteland Tower, on the higher elevations.
With a health of 144 HP, they nearly three times as strong as the base Moblin and a little less than have as powerful as the Black Moblin. Like the standard Moblin, they will drop Moblin Horns and Moblin Fangs when defeated. However, the blue variation will also occasionally drop Moblin Guts.
Hyrule Compendium entry of the Blue Moblin.