First, you have to create a new 10*10 psd file with transparent background color.

Then, zoom in to a certain size with the navigator (size according to your own visualization)

Next, draw a rectangular selection box with the rectangle selection box tool and fill it with white.

Secondly, select Menu - Modify Command - Shrink to bring up a dialog box and modify the shrink size according to your needs. (You can try 3 pixels)

Then, ctrl+a to select the whole layer. Edit menu - Define Pattern command,

Finally, create a new psd file, fill the background with red color and create a new layer. Fill layer one with a pattern, (the filled pattern is the graphic one we just made) and then modify the transparency of layer one.

Then it's done.

I say trouble, but you do it to know, in fact, very simple.