If you know the dimensions of your garage, you can just plug them into the Swisstrax Designer. From there you can figure out how many edges you need and how many of each color. As well as play around with the design to see what you like. Once you have something set, send us some screenshots and more info of your garage and we can look it over to make sure you'll have everything you need. Here's a sample of what a 20x20 two-car garage would look like:
For a garage that size, here's what you'll need:
Here are the tile counts, though I would add about 5 extra onto the Slate Grey. Since you'll be making cuts around the walls, you may need some extras just in case. You'll want Looped Edges, and the count there is correct to give you a couple extra.