I'm trying count the number of cells with the same background color and put the result in other cell with a script in google apps script, but I can't do it. I have the next script but not work and I don't know which is the problem:

```
function countbackgrounds() {
 var book = SpreadsheetApp.getActiveSpreadsheet();
 var range_input = book.getRange("B3:B4");
 var range_output = book.getRange("B6");
 var cell_colors = range_input.getBackgroundColors()[0];
 var color = "#58FA58";
 var count = 0;

 for( var i in cell_colors )
  if( cell_colors[i] == color ){
    range_output.setValue(++count);
  }
  else {
    return count; 
  }
 }  

```