The label on the bottle says it is "navy" blue, but it seems like you've added half the bottle before it bears the slightest resemblance to the colour you're aiming for - don't get blue!
There's a trick to navy blue, and it is called black. And patience. Okay, not very magical. But there you have it - it works : )
So, If you are using gel food colour to get navy royal icing - add a drop or two of black (not too much) - it may not look very navy at first (more like a dark blueck!), but leave it overnight and that brooding blue will have a chance to come out of its shell and show its true colours - you'll be pleasantly surprised at the result.
Octopus design inspired by Yankee Girl Yummies (and her octopus did have 8 legs - a true professional!)
Beach scene from a tutorial by the amazing Amber of Sweetambs.