The icons you see at %pmllib%\icons\styles are only images representing the macro of each hatch patterns.
So when you edit the image through Paint, you have just edit the image but not the macro.
I never try create my own hatch, you may give a try creating your own.
Try read and understand the procedure on this manual:
C:\AVEVA\Plant\PDMS12.0.SP6\Manuals\Docs\DRAFT User Guide.pdf Chapter 8.4.2 User-Defined Fill Styles
The icons you see at %pmllib%\icons\styles are only images representing the macro of each hatch patterns.
So when you edit the image through Paint, you have just edit the image but not the macro.
I never try create my own hatch, you may give a try creating your own.
Try read and understand the procedure on this manual:
C:\AVEVA\Plant\PDMS12.0.SP6\Manuals\Docs\DRAFT User Guide.pdf Chapter 8.4.2 User-Defined Fill Styles