In some places in The Hobbit: An Unexpected Journey, 'Sting', (Bilbo's sword) wasn't glowing blue. There are a few scenes where Bilbo is around Orcs, Even one where they were fighting the Pale Orc, but the sword was still not shown to glow.
Sting had the magical ability to detect orcs or goblins nearby. When orcs or goblins were present, it glowed blue, as it did when the Fellowship encountered orcs in the mines of Moria. This was a common property of First Age Elf blades, particularly those forged in Gondolin.
So if I'm not blind, is there some explanation for that or is it just a mistake?