Fix broken legend color (Fixes #915) + add stroke transparent
Fix broken legend color (Fixes #915) + add stroke transparent

uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,uwdata/vega-lite,vega/vega-lite,vega/vega-lite,vega/vega-lite