gistfile1.coffee

....
features = [List-with-FeaturePoints-generated-on-the-client]

vectorSource = new ol.source.GeoJSON(({
  "object":
    "type": "FeatureCollection"
    "features": features
}));

vectorLayer = new ol.layer.Image({"source": new ol.source.ImageVector(
  source: vectorSource
  style: (feature) ->
    
    prop = feature.getProperties();
    fillColor = prop.color

    if !fillColor
      ft = [0,0,0,0]
    else
      ft = fillColor.split("(")[1].split(")")[0].split(",")
      ft.push(1)

    baseStyle = {
      fill: new ol.style.Fill({
        color: "rgba(#{ft[0]},#{ft[1]},#{ft[2]},#{ft[3]})"
      })
      stroke: new ol.style.Stroke(
        color: "rgba(#{ft[0]},#{ft[1]},#{ft[2]},#{ft[3]})"
        width: 1
      )
    }

    if prop.line > 0
      baseStyle.stroke = new ol.style.Stroke(
        color: "#333"
        width: prop.line
      )

    return [new ol.style.Style(baseStyle)]

)});

_that._clearLayerGroup('gridlayer')
targetGroup.getLayers().push(vectorLayer)

....