Tile is not my speciality but i would suggest finding a local tile guy who only deals with tile. These big box stores carry lots of products but can really lack when it comes to speciality items like dark blue grout. That seems like an odd item for them to carry on the regular.

I also know you can buy like a grout dye or paint i dont know exactly what its called but basically you apply this stuff over grout to get a desired color.

But im a hardwood guy not a tile guy. Good luck.

We recently had our pool remodeled and the pool supply company where we chose our tile had all different shades of blue grout. So you might try a place that specializes in pool tiles and plaster. They have lots of blue grout to go with the pools.

You might have better blue selections as TXBluebonnet11 suggested, but in the Custom brand regular tile grout full sample deck, there is a dark blue grout that is more of a navy, called Admiral Blue, #92. Link below to their full color chart. This is available in sanded or unsanded grout with caulk to match I believe like their other 48 colors. The big box stores typically carry just the most popular and best selling colors so your color choices are limited there. The link below is their full brochure explaining the different grout types and choices and has the color chart at the end. It is way off for the blues (that typically have trouble reproducing the actual color in print). The Admiral blue from my grout sample deck is more navy and not almost black. And the Ocean Blue is more mid value grey blue and not a bright cobalt blue as the printed chart shows and the Artic Blue is a pale blue grey and not just pale grey as the chart shows.

On their website, go to the "Where to Buy" or the "Distributors" tab to find where to buy in your area. The blues will most likely not be a stock color but they can order it. They should also have a sample deck or even just individual 'sticks' to give or sell to you so you can check a more accurate color with your tile. And their main number is 800.272.8786.

Good luck and let us know of your progress.

Here is a link that might be useful: Custom Polyblend grout brochure

I just noticed I had an older Custom grout sample deck with two more blues. These are most likely discontinued but they might still be available in a warehouse and a tile place might have one of these older sets. The Admiral Blue is new, so if their deck has that, it is the newer deck. The older one has two brighter blues, but lighter than the Admiral. There is Midnight Blue #405 that is a dark periwinkle blue (purple/blue) and a Captain's Blue #387 that is a dark Wedgwood blue (clear mid color blue). Thought this might help if one of these would work. I have found and used discontinued items before and sometimes it's just what you need.

There are other regular tile grout brands also, this is the most available one to me. So you can look up Laticrete, Bostik, TEC, Ardek and probably others. But be sure to not just go by the printed color chart in the brochure but actual samples which are a more accurate plastic 'sticks' that you can hold next to the tile. These are in a kit with all the colors or individual pieces. Color matched caulk may or may not be available in these other brands so if that is important to you, check that out.

Good luck!

Hi
I found it on Home Depot Online. Cannot get it in the store but can be picked up in the store when it comes in
Good Color for Blue Mosaic Designs
L