I am making a swimming pool cake for my daughters high school swim team banquet and I need help with a few details. This cake needs to be done tonight so if anyone could help - I would really appreciate it. Here are my questions:

1. What colors mix together to make Navy Blue?
2. Do I pipe the lane lines before or after I fill the pool with piping gel?

These may sound like simpe questions, but I am very new at this and still learning. Thanks for any help!

If I needed to make a darker blue I'd add a drop of black to the darkest blue I had. For the pane lines I'd pipe them on after.
Someone else may have other thoughts