Well I have a sky blue hobo and i just looked at it, it looks like the same colour. The sky blue sample on http://ateliernaff.blogspot.com looks a little grayer than it really is.
IF it is that bag, I suggest you go for it becuase as you know Balenciaga's new leathers are not as gorgeous as the older ones (the new ones are shinier). This seasons are buttery soft, infact unbelievably creamy. It's what makes balenciaga so great!
If it is a Balenciaga, I would guess sky blue. Although, I have seen some cornflower bags photograph much lighter than they are IRL. I think we need to see the entire bag and the metal tag to be able to render an informed verdict.