-

<Map srs="+init=epsg:3857">
    <Style name="geoms">
        <Rule>
            <Filter>[mapnik::geometry_type]=linestring or [stroke] != null</Filter>
            <LineSymbolizer stroke="[stroke]" stroke-width="[stroke-width]" />
        </Rule>
        <Rule>
            <Filter>[mapnik::geometry_type]=polygon or [fill] != null</Filter>
            <PolygonSymbolizer fill="[fill]" fill-opacity="[fill-opacity]" />
        </Rule>
    </Style>
    <Style name="points" filter-mode="first">
        <Rule>
            <Filter>[mapnik::geometry_type]=point and [marker-path]</Filter>
            <MarkersSymbolizer
              file="[marker-path]"
              width="80"
              allow-overlap="true"
              ignore-placement="true"
            />
        </Rule>
    </Style>
    <Layer name="layer" srs="+init=epsg:4326">
        <StyleName>geoms</StyleName>
        <StyleName>points</StyleName>
        <Datasource>
            <Parameter name="type">geojson</Parameter>
            <Parameter name="inline"><![CDATA[{"type":"FeatureCollection","features":[{"type":"Feature","geometry":{"type":"Point","coordinates":[-73.99,40.7]},"properties":{"marker-color":"7e7e7e","marker-size":"large","symbol":"-","marker-path":"/var/folders/lh/rwmhbvnd5rdc2qc5t5n2pv4w0000gn/T/geojson-mapnikify-51b5018a7686a008056feff570d49926.png"}},{"type":"Feature","properties":{"marker-color":"#3887be","marker-size":"medium","symbol":"-","id":"marker-marker-hzu8pcp622","title":"Welcome to Mapbox!","description":"","marker-symbol":"embassy","marker-path":"/var/folders/lh/rwmhbvnd5rdc2qc5t5n2pv4w0000gn/T/geojson-mapnikify-59cb59ca8660c60ee7e28573006a5514.png"},"geometry":{"type":"Point","coordinates":[-122.41940307617188,37.774898529052734]}}]}]]></Parameter>
        </Datasource>
    </Layer>
</Map>

Results in:

[Tue, 09 Sep 2014 21:56:15 GMT] [error] [default] Error: Failed to parse color: "[stroke]" in style 'geoms' in LineSymbolizer