I was recently involved in a project that had a lot of different countries particularly scandinavian and neede som flags for the different countries. I been looking into using font files for icons and such for a while so I thought "now not give flags a go" untill I remembered that flags er multicolor so it need to be a combination of font icon and css to get it to work.
Eventually I mangede to get the results I wanted using this technique which now enables you to control the font size and get infinite resolution sized flags. You can see the result here
A good utility for the font file creation was the App a IcoMoon. Give it a go at https://icomoon.io/app/ . It's really great at creating a combined file from multiple SVG files.