Flexi Custom Code - Awesome PHP Code Insertion Module

Today I will introduce a free module for adding PHP, HTML, CSS or JS code.
Unfortunately the developer of this module has stopped working, but it still works on Joomla 4 - Simply because this module is not complicated.
I have used many Custom modules, but this is the only one that supports PHP language. Make you comfortable to customize the website (Of course if you know PHP - LOL).
This module is now out of JED, fortunately I have a backup. You can download it below:
Flexi Custom Code - Joomla 3 & 4 Flexi Custom Code - Joomla 2.5
I will have a series of articles related to PHP and will use this module.
I have been googling how to change the menu colours, as the black text on my purple background is not very readable. However everything I have tried to change the text colour of the Off-Canvas main menu text to white did not work.
Would you know what custom CSS I would need to change all menu items to white text (including submenus).
Probably need background colour to not be white when hovering over submenus
Any help you can provide would be gratefully appreciated (or a pointer to some useful help).
Thank you
see
https://siteupdate.vedicmaths.org/index.php
InPre-Update Check for Joomla 5.4.4
for Off-Canvas it says
Joomla cannot detect the extension's compatibility with the target version of Joomla.
have you implemented the compatibility stuff for Joomla to upgrade extensions correctly ?
Have got two off canvas menus working (1. for tools and 2. for main menu)
However I can only get the Main menu to display the first level of menu items.
Have you any suggestions for getting the sub menu items to display ?
N.B. the menu item with sub menu items does display a down arrow, but trying to click on it only display the item at the main menu level.
see
https://siteupdate.vedicmaths.org/index.php
If you want to see where I have currently got to