Add a custom field in Woocommerce Edit Account pag

I have custom checkout fields favorite_color that users can fill in during checkout (not required),imilar to other default checkout fields...

In My Account section in "Edit Account", I Would like to add favorite_color custom field to allow customer editing this field value.

For that I have edited the template myaccount/form-edit-account.php by copying and editing an original line of code in it:

    <p class="woocommerce-form-row woocommerce-form-row--first form-row form-row-first">
    <label for="account_first_name"><?php _e( 'First name', 'woocommerce' ); ?> <span class="required">*</span></label>
    <input type="text" class="woocommerce-Input woocommerce-Input--text input-text" name="account_first_name" id="account_first_name" value="<?php echo esc_attr( $user->first_name ); ?>" />
</p>

I replaced the account_first_name with my favorite_color and the field even shows the saved value in the field (thanks to $user->favorite_color)

But the bad part is, it does not get saved.

What code must I add to get this working and getting saved?

The original template code is:

<?php
/**
 * Edit account form
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/myaccount/form-edit-account.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see     https://docs.woocommerce.com/document/template-structure/
 * @author  WooThemes
 * @package WooCommerce/Templates
 * @version 2.6.0
 */

if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

do_action( 'woocommerce_before_edit_account_form' ); ?>

<form class="woocommerce-EditAccountForm edit-account" action="" method="post">

    <?php do_action( 'woocommerce_edit_account_form_start' ); ?>

    <p class="woocommerce-form-row woocommerce-form-row--first form-row form-row-first">
        <label for="account_first_name"><?php _e( 'First name', 'woocommerce' ); ?> <span class="required">*</span></label>
        <input type="text" class="woocommerce-Input woocommerce-Input--text input-text" name="account_first_name" id="account_first_name" value="<?php echo esc_attr( $user->first_name ); ?>" />
    </p>
    <p class="woocommerce-form-row woocommerce-form-row--last form-row form-row-last">
        <label for="account_last_name"><?php _e( 'Last name', 'woocommerce' ); ?> <span class="required">*</span></label>
        <input type="text" class="woocommerce-Input woocommerce-Input--text input-text" name="account_last_name" id="account_last_name" value="<?php echo esc_attr( $user->last_name ); ?>" />
    </p>
    <div class="clear"></div>

    <p class="woocommerce-form-row woocommerce-form-row--wide form-row form-row-wide">
        <label for="account_email"><?php _e( 'Email address', 'woocommerce' ); ?> <span class="required">*</span></label>
        <input type="email" class="woocommerce-Input woocommerce-Input--email input-text" name="account_email" id="account_email" value="<?php echo esc_attr( $user->user_email ); ?>" />
    </p>

    <fieldset>
        <legend><?php _e( 'Password change', 'woocommerce' ); ?></legend>

        <p class="woocommerce-form-row woocommerce-form-row--wide form-row form-row-wide">
            <label for="password_current"><?php _e( 'Current password (leave blank to leave unchanged)', 'woocommerce' ); ?></label>
            <input type="password" class="woocommerce-Input woocommerce-Input--password input-text" name="password_current" id="password_current" />
        </p>
        <p class="woocommerce-form-row woocommerce-form-row--wide form-row form-row-wide">
            <label for="password_1"><?php _e( 'New password (leave blank to leave unchanged)', 'woocommerce' ); ?></label>
            <input type="password" class="woocommerce-Input woocommerce-Input--password input-text" name="password_1" id="password_1" />
        </p>
        <p class="woocommerce-form-row woocommerce-form-row--wide form-row form-row-wide">
            <label for="password_2"><?php _e( 'Confirm new password', 'woocommerce' ); ?></label>
            <input type="password" class="woocommerce-Input woocommerce-Input--password input-text" name="password_2" id="password_2" />
        </p>
    </fieldset>
    <div class="clear"></div>

    <?php do_action( 'woocommerce_edit_account_form' ); ?>

    <p>
        <?php wp_nonce_field( 'save_account_details' ); ?>
        <input type="submit" class="woocommerce-Button button" name="save_account_details" value="<?php esc_attr_e( 'Save changes', 'woocommerce' ); ?>" />
        <input type="hidden" name="action" value="save_account_details" />
    </p>

    <?php do_action( 'woocommerce_edit_account_form_end' ); ?>
</form>

<?php do_action( 'woocommerce_after_edit_account_form' ); ?>

This can be done without overriding template files, just using available hooks this way:

// Add the custom field "favorite_color"
add_action( 'woocommerce_edit_account_form', 'add_favorite_color_to_edit_account_form' );
function add_favorite_color_to_edit_account_form() {
    $user = wp_get_current_user();
    ?>
        <p class="woocommerce-form-row woocommerce-form-row--wide form-row form-row-wide">
        <label for="favorite_color"><?php _e( 'Favorite color', 'woocommerce' ); ?>
        <input type="text" class="woocommerce-Input woocommerce-Input--text input-text" name="favorite_color" id="favorite_color" value="<?php echo esc_attr( $user->favorite_color ); ?>" />
    </p>
    <?php
}

// Save the custom field 'favorite_color' 
add_action( 'woocommerce_save_account_details', 'save_favorite_color_account_details', 12, 1 );
function save_favorite_color_account_details( $user_id ) {
    // For Favorite color
    if( isset( $_POST['favorite_color'] ) )
        update_user_meta( $user_id, 'favorite_color', sanitize_text_field( $_POST['favorite_color'] ) );

    // For Billing email (added related to your comment)
    if( isset( $_POST['account_email'] ) )
        update_user_meta( $user_id, 'billing_email', sanitize_text_field( $_POST['account_email'] ) );
}

Code goes in function.php file of your active child theme (or active theme) or in any plugin file.

Tested and works.

If you want to override the template to display the custom field, you just have to keep the 2nd hooked function (the one who saves the data when edited).