SumByColor.js

function getBackgroundColor(rangeSpecification) {
  var sheet = SpreadsheetApp.getActiveSpreadsheet();
  return sheet.getRange(rangeSpecification).getBackground();
}

function getForegroundColor(rangeSpecification) {
  var sheet = SpreadsheetApp.getActiveSpreadsheet();
  return sheet.getRange(rangeSpecification).getFontColor();
}


function sumWhereBackgroundColorIs(color, rangeSpecification) {
  var condition = function (cell) { return cell.getBackground() == color; };
  return sumByCondition(color, rangeSpecification, condition);
}

function sumWhereBackgroundColorIsNot(color, rangeSpecification) {
  var condition = function (cell) { return cell.getBackground() != color; };
  return sumByCondition(color, rangeSpecification, condition);
}

function sumWhereForegroundColorIs(color, rangeSpecification) {
  var condition = function (cell) { return cell.getFontColor() == color; };
  return sumByCondition(color, rangeSpecification, condition);
}

function sumWhereForegroundColorIsNot(color, rangeSpecification) {
  var condition = function (cell) { return cell.getFontColor() != color; };
  return sumByCondition(color, rangeSpecification, condition);
}




function sumByCondition(color, rangeSpecification, condition) {
  var sheet = SpreadsheetApp.getActiveSpreadsheet();
  var range = sheet.getRange(rangeSpecification);
  
  var x = 0;
  
  for (var i = 1; i <= range.getNumRows(); i++) {
    for (var j = 1; j <= range.getNumColumns(); j++) {
      
      var cell = range.getCell(i, j);
      
      if(condition(cell)) {
        var cellVal = parseFloat(cell.getValue());
        if (isFinite(cellVal))
          x += cellVal;
      }
    }
  }
  
  return x;
}