You can also play around with the stroke-width of the circle to make it stand out a little more on lighter colors:
<circle cx="280" cy="14" r="20" stroke="black" stroke-width="7" fill="white" />

Granted I get that not everyone will still be able to see that well, but that’s the beauty of having the code so it can be played around with.
I’ve made mine gray scale so it better fits in with my dark theme

Thanks to @TanelTM for sharing this with us.