food for thought, some formulas from the Union Mixopake sytem which may give you some insight even though you don't have these ingredients.
To make an ink that matches Union light navy (which is regular navy to everyone else) they use close to
50 parts Blue (Green shade)
30 Violet (Which is almost identical to their stock Purple)
20 Black
To make Royal they use
83 Blue (G/S)
17 Violet
So, to me it looks like a little Purple will help as well.
Like was mentioned, start small, literally toothpick or matchstick quantities to get started aren't that crazy in these endeavors