You can add the fill-opacity attribute to the <path/>. It takes a value from 0.0 (transparent) to 1.0 (opaque).
Example (0.5 50% transparent):
<path fill="blue" fill-opacity="0.5" d="m-101.116-101.116m169.705........" />
Remember though that this will show red if fully transparent as that is the color the blue area is over. If you want that area to also be transparent you’ll need to do a bit more work.