This should be pretty easy to reproduce, since that’s how I did it. Seen others do it and copied but seemingly, not as simple as I thought it was.
1. Start off by opening whatever file you wanna add a border too, I have a normal 450*150 signature sized one. Make sure you have your 2 colors ready to use, I’d suggest Black + Color cause they always look best with black but feel free to experiment.
2. Make a new layer called “Border” and fill it with black (Or your primary color).
3. This is where it gets technical (barely). Select your whole layer by pressing CTRL + A or going to Select > All. Then go to Select > Shrink > 1 px. > Ok.
4. Once you’ve shrunken your border selection, fill in with White (or your secondary color). Then repeat Select > Shrink > 1 px. > Ok.
5. Once you’ve shrunk it one more, fill in your selection with Black again (Or primary color). Then Select > Shrink > 1px. Ok once more and after shrinking, press CTRL + X or go to Edit > Cut to cut your file to have a transparent border.
6. Now that you’re all finished, fill in the center with a gradient (using a new layer of course).
This part here now is for anyone who likes my old blurry border, I personally find the first one better but you never know.
1. Repeat Steps 1-3 from the first tutorial
2. Once you’re done with that repeat Step 5 from the first tutorial, you should have a plain black border and a transparent background. Duplicate it.
3. Once duplicated, go to Filters > Blur > Gaussian Blur > 10 px. > Ok.
4. When you’re done, duplicate the blurred layer for a darker tone.
5. Final Result