Adding style to SVG
<?xml-stylesheet href="styles_austria_1.css" type="text/css"?>
Here's what an SVG CSS file looks like.
.str1 {stroke:#0093DD;stroke-width:16;color:#0093DD} .str2 {stroke:#0093DD;stroke-width:12} .str3 {stroke:#0093DD;stroke-width:10} .str4 {stroke:#0093DD;stroke-width:6} .str0 {stroke:#DA251D;stroke-width:55;color:#DA251D} .str6 {stroke:#BB90BB;stroke-width:44;color:#BB90BB} .str5 {stroke:#0093DD;stroke-width:4} .str7 {stroke:#1F1A17;stroke-width:13} .fil0 {fill:none} .fil2 {fill:#1F1A17} .fil1 {fill:#C4E5FA} .fil3 {fill:#FFFFFF}
Source: Example for using CSS-Styles [carto.net]
Reference: Styling - SVG 1.1 - 20030114 [w3.org]