Thanks for the link, it was some good information.
I think I have the mix now. I used the wicked detail Cobalt blue 13 drops and 2 drops wicked black. 3 coats and I'm at my dark blue. The key was being able to repeat the color.
The wicked blue when mixed with black had a green hue. The cobalt had more of a blue hue. As the layers built up it became a darker blue.
My problem was making big jumps in adding color and not making small adjustments.
So the link was helpful, thank you.