Those are 1-pixel wide translucent pink lines, so:
1. Color pick from the area in the middle with the whitest background.
2. Draw a 1 pixel wide line, copy-paste the line and space the lines out properly (9 pixels), until you have covered the desired area.
3. Adjust transparency.
4. Adjust color. (This probably means you have to darken the color because reducing transparency makes the color lighter.)