test.carto

@color: hsl(30, 40%, 90%);

#world {
  polygon-fill: green;
  building-fill: darken(green, 10);
  line-color: @color;
  line-width: (1+3)*4;
}

test.xml

<?xml version="1.0" encoding="utf-8"?>
<Map srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
    <Style name="#world" filter-mode="first">
        <Rule>
            <PolygonSymbolizer fill="#008000"/>
            <BuildingSymbolizer fill="#004d00"/>
            <LineSymbolizer stroke="#f0e6db" stroke-width="16"/>
        </Rule>
    </Style>
</Map>