Mage::helper('stackexchange_freeshipping')->__(
                'Your cart has the has the value of %s. In order to get free shipping you need to order for %s more',
                '<span style="color:green">'.Mage::helper('core')->currency($subtotal, true, false).'</span>',
                '<span style="color:red">'.Mage::helper('core')->currency($freeShippingValue - $subtotal, true, false).'</span>'
            )