COUNTCOLOR.js

// Script for Google Spreadsheet
//
// Counts the number of cells inside countRange (string) 
// which have the same color as the cell pointed out by
// colorRef (also as string). If a cell is merged then
// they are counted as mergeWeight cells instead of 1.
function COUNTCOLOR(countRange,colorRef,mergeWeight,_) {
  var activeRange = SpreadsheetApp.getActiveRange();
  var activeSheet = activeRange.getSheet();
  var range = activeSheet.getRange(countRange);
  var colorCell = activeSheet.getRange(colorRef);
  var color = colorCell.getBackground();
  var count = 0;
  for(var row = 1; row <= range.getNumRows(); row++) {
    for(var column = 1; column <= range.getNumColumns(); column++) {
      cell = range.getCell(row, column)
      if (cell.getBackground() == color) {
        count += (cell.isPartOfMerge() ? mergeWeight : 1)
      }
    }
  }  
  return count;
};