Openlayers set color as attibute for stylemap

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/openlayers/2.13.1/OpenLayers.js"></script>
<script src="https://www.openstreetmap.org/openlayers/OpenStreetMap.js"></script>
 Example for answer to question on stackexchange ( <a href="https://gis.stackexchange.com/questions/206500/keep-circle-color-when-overlaping-on-openstreetmaps" target="_blank">https://gis.stackexchange.com/questions/206500/keep-circle-color-when-overlaping-on-openstreetmaps</a>)
<div id="map"></div>

CSS

html,
  body,
  #map {
    height: 90%;
    margin: 0;
  }

JavaScript

var map;
 var standard_zoom = 10;
 var all_layers = [];

 var standard_style = {
   strokeColor: 'black',
   strokeOpacity: 1,
   strokeWidth: 2,
   fillOpacity: 0.2,
   fillColor: "${color}"
 }

 function init() {
   map = new OpenLayers.Map("map", {
     controls: [
       new OpenLayers.Control.Navigation(),
       new OpenLayers.Control.PanZoomBar(),
       //new OpenLayers.Control.LayerSwitcher(),
       new OpenLayers.Control.Attribution()
     ],
     maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
     maxResolution: 156543.0399,
     numZoomLevels: 19,
     units: 'm',
     projection: new OpenLayers.Projection("EPSG:900913"),
     displayProjection: new OpenLayers.Projection("EPSG:4326")
   });

   // Define the map layer
   // Here we use a predefined layer that will be kept up to date with URL changes
   map.addLayer(new OpenLayers.Layer.OSM.Mapnik());
    addCircle(8.7321,50.0,10000, 'red');
   setCenter(8.7321,50.0,10);
 }

 function setCenter(lng,lat, zoom) {
   map.setCenter(
     new OpenLayers.LonLat(lng || -47.9355023, lat || -15.7603797).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject()),
     zoom || 5
   );
 }

 function addCircle(lng, lat, radius, color) {
   var lonLat = new OpenLayers.LonLat(lng, lat).transform(
     new OpenLayers.Projection("EPSG:4326"),
     map.getProjectionObject()
   );

   var layer = new OpenLayers.Layer.Vector("", {
     styleMap: new OpenLayers.StyleMap(
       standard_style
     )
   });
   var point = new OpenLayers.Geometry.Point(lonLat.lon, lonLat.lat);
   var circle = OpenLayers.Geometry.Polygon.createRegularPolygon(point, radius, 40, 0);



   layer.addFeatures([new OpenLayers.Feature.Vector(circle,

     {
       name: "ich_brauch_vielleicht_keinen_namen",
       color: color
     }
     //, standard_style
   )]);
   map.addLayer(layer);
   all_layers.push(layer);
 }

 function removeLayers() {
   while (all_layers.length > 0) {
    ...