Image collage - card outline

I would like to make the cards (not the images) have an outline when I use image:collage. I don't want to do this block by block; I want code that will make all of them have that outline. Any ideas?

Can you please share site url?

https//www.cherrytreeinteriordesign.com

3 hours ago, CherryTree said:

https//www.cherrytreeinteriordesign.com

.fe-block-0f1b481d6096757f0edf {
  border-style: solid;
  border-color: red;  /*change color here*/
}

Use class .fe-block check attachment 

But won't that just be for a specific block? I want to have it for all blocks like that, because there are too many and I don't have the time to specifically target each one.

I'm trying to make the collage text look like the attached photo for all of them. It's for my blog, so it's classic editor. Each blog post has 8-10 photos and is ongoing, so it will not work to do it block by block. I found a tutorial that almost works, but it's assuming that the caption be larger than the photo (which I don't want), and something in it is broken and makes the image disappear anyway. The almost-code is here: https://insidethesquare.co/squarespace-tutorials/collage-image-borders

I need something like that in that it applies to all the blocks universally, but it needs to look like the attached photo instead.