It could be done IF you have the right kind of clay, a kiln, and the necessary expertise to color and form the raw tile. Hopefully you understand that the tile has to be baked at high temperatures. I don't know the exact temp but I believe it is well over 1,000 degrees for several hours. Find a pottery maker in your area and talk to them.

It's certainly possible, if you've got the resources that Bob mentioned, but I wouldn't plan on making tile to match the commercially-produced tile you've already got. It's not as if tile producers publish their glazing methods and recipes. Also, plan on it being fairly expensive compared to the mass-produced product.

I had a friend who made a couple of decorative "handprint" tiles of her children at one of those "make your own pottery" studios. They were a charming and fun accent to her kitchen backsplash, but even in plain "white", they were difficult to actually "match" to the field tile she used as the main tile. Look on the Decorating Forum or Kitchen Forum for the thousand and one threads asking about "which white" to pick out or match to see what I mean about how difficult it is to even match such a "simple" color. Making something to match a commercially produced tile instead of taking the home made item and trying to match it would likely be a huge exercise in futility and expense.

If your tile is a solid body porcelian, or the tile back is very similar to the front, you *may* be able to create bullnose trims with a grinder.

But there are so many tens of thousands of choices in tile, I'm pretty sure you can find something you like if you keep looking.

Go to the websites of the major companies like Crossville, Daltile, American Olean, etc., or visit the actual tile sellers in your area, vs. the big boxes.