Set session time (save text color for a specific time)

There is file.html

<form method="post" action="file.php"> <p> <select size="5" name="color"> <label>Цвета</label> <option value="red">Красный</option> <option value="blue">Синий</option> <option value="yellow">Жёлтый</option> <option value="brown">Коричневый</option> <option value="green">Зелёный</option> </select> </p> <p><input type="submit" name="submit" value="Выбрать"></p> </form> 

And file.php

 <?php session_start(); if (isset($_POST['submit'])){ if (!empty($_POST['color'])){ $_SESSION['color'] = $_POST['color']; } } $color = $_SESSION['color']; ?> <div> <font color="<?php echo $color?>"> Some text here..... </font> </div> 

How to make the text color saved only 1 minute in the browser after submitting the color?