Okay, I figured it out. I took screen capture of another cursor, opened it in PS, selected background and then inverse, changed colors and saved it to same name as cursor I'm replacing, copied this to Theme folder in CursorFX folder and then imported it within editor with cursor to be replaced highlighted, then save. Finally, apply cursor again to change to take effect. Done!
I notice that when re-applying settings, changes such as brightness and size are lost as applying cursor starts with default setting.