I did something similar, but in my case, the color also came from the data, but that will help you. You must override the Datagrid and override the drawRowBackground method.
public class CustomDataGrid extends AdvancedDataGrid
{
protected override function drawRowBackground(s:Sprite, rowIndex:int, y:Number, height:Number, color:uint, dataIndex:int):void{
var XMLdata:XML=rowNumberToData(dataIndex) as XML;
if(XMLdata!=null){
if(XMLdata.attribute(Constants.col) != undefined && XMLdata.attribute(Constants.col) != ""){
color=XMLdata.attribute(Constants.col);
}else{
color=0xFFFFFF;
}
}
super.drawRowBackground(s,rowIndex,y,height,color,dataIndex);
}
}
.