A Google Spreadsheet Function to count number of cells in a column which all are used selected background colors.

script.js

/*
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  Returns total number of rows for selected background colors separated by comma, in a column range.
	
  @ param string  colors - A set of background hex colors separated by comma. Ex: '#ff0000,#000000,#AEAEAE'
  @ param string rangeSpecification - Column field range of rows. Ex: 'E1:E20' 
  @ return int number of rows with colors listed background colors.
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*/
function countCellsWithBackgroundColors(colors, rangeSpecification) {

  var sheet = SpreadsheetApp.getActiveSpreadsheet();
  var backGroundColors = sheet.getRange(rangeSpecification).getBackgrounds();
  var colorArray = colors.split(",");
  var x = 0;

  for (var i = 0; i < backGroundColors.length; i++) {
    for (var j = 0; j < backGroundColors[i].length; j++) {
      for (var c = 0; c < colorArray.length; c++) {
        if (colorArray[c] == backGroundColors[i][j]) {
            x++;
        }
      }
    }
  }
  return x;
}