The expected style for macOS menu bar images is a template image than
can adapt to the user's appearance settings. Also, high-res screens
("Retina" in Apple speak) need higher resolution images.
Based on /res/barrier.svg, I created black and transparent SVGs for the
three icon states. I had to remove some details to make the image scale
down to icon size without becoming too crowded, and I drew a new
checkmark and the transfer arrow.
Daniel Seither