gsheet get cell background color
/**
* Returns the Hexadecimal value of a cell's background color.
*
* @param {number} row The cell's row number.
* @param {number} column The cell's column number.
* @return The Hexadecimal value of the cell's background color.
* @customfunction
*/
function BGHEX(row, column) {
var background = SpreadsheetApp.getActive().getDataRange().getCell(row, column).getBackground();
return background;
}