I'm a big fan of van courtland blue (HC-145) and wedgewood gray (HC-146). My favorite is philipsburg blue (HC-159) but it'll probably be too dark for you. Both VCB and WG look great with navy and dark brown. I'd recommend a test of them under your lighting conditions in the actual paint that will be used on your walls (sheen can make a big difference).

Below is a picture of BM Hudson Bay on one wall of my daughters dining room. She used that color as an accent on that wall and one wall of her adjoining living room. In real life the blue is a little darker than in the picture. I think it is a very dramatic and rich looking color. She used BM Stonington gray on the rest of the walls.
{{!gwi}}

This may be a little dark, but check it out. We used charlotte slate in our kid's bathroom upstairs. I LOVE the color. No one loved it as much as me. I would consider painting cabinets that color, that is how much I loved it. It's a lovely medium blue gray. Incidentally, we are repainting the bathroom in orange ice for a refresh. :) There may be a lighter version above it that you may like on that color swatch. I can't remember where I put my deck or I'd look it up for you.
Kim

I second Wedgewood Grey - it's such a beautiful color!!

I use BM Serenata in my bathroom and it is so beautiful, not dark an not light. Just perfect :-)

I like mt. rainier gray, 2129-60. It has a pretty blue undertone on the wall that will blend beautifully with navy.

All my blues are Sherwin Williams. If that can be helpful, let me know and I'll share.

We have BM Nantucket Fog in our mudroom and bedroom. I'm a big fan. It's a medium blue with a lot of gray in it, so it definitely doesn't read as baby blue. Sorry for the cell phone picture, but it will give you an idea. There's a mudroom photo in that photo set too, but that lighting is also pretty bad. We've drywalled the ceiling and added trim since then!

i will post a pix. tom. when my bed is made, but i have BM AURA line of paint in tranquility, beautiful soft blue, but not a baby blue at all, everyone who see's it loves it.

Our kitchen remodel town home renovation is in the cyclone phase to finish up. Actual conversation with GC today:
GC: stopped and left tile. What happened to painting sage green?
Me: I changed my mind. Wanted more a coastal feel.
GC: well I told clients you were doing this awesome green.
Me: no. I'm doing this awesome blue instead...
Which happens to be wedgewood gray so hopefully I'll have pics to post but a lot of pics come up with a google search.

kawcjp mentioned Philipsburg Blue (hc-159) as a favorite, we used it in a remodel a couple of years ago. Sorry, but you'll have to click through to photo #6, too lazy to go through Photobucket right now... One note, this house has a lot of light so a dark color wasn't oppressive.

Here is a link that might be useful: hc-159 paint photo #6