SVG icons via data uri. No sprite sheet, no external resource, no repeated code.
The marker icon has no colour attribute, that comes from CSS.
This is a combination of other techniques. Most notable: https://css-tricks.com/probably-dont-base64-svg/ and https://codepen.io/noahblon/post/coloring-svgs-in-css-background-images
I just brought these two together into a :before pseudo element where they could be targeted.