Sum a column in google doc spreadsheet if it matches a certain background color

sumifcolor.js

function sumIfColor() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheets()[0];
  var nrows = sheet.getMaxRows();

  var color_cell = Browser.inputBox("Cell with background color to use?");
  var output_cell =  Browser.inputBox("Output cell? (Eg. D3)");
  
  var color_match = sheet.getRange(color_cell).getBackgroundColor();
  
  var r=1;
  var sumgreen=0;

  while (r<nrows) {
    var c = 1;

    var color = sheet.getRange(r,c).getBackgroundColor();

    if(color==color_match) {
      sumgreen ++;
    }
    r++;
  }
  sheet.getRange(output_cell).setValue(sumgreen);
}