toggle a color section when a button is clicked doesn´t work

Do you load jQuery in footer? if you do – then it might be good to set on

add_action('wp_footer', 'toggle_on_click', 999);

a priority to be sure that your script loads after jQuery.

next ( please change that on documentation page too ) : on newer jQuery Versions the :

jQuery(window).load(function(){	

is deprecated – you had to use now:

$(window).on('load', function(){

By the way: the display : none is a toggle between two states – so it is not animatable.
The toggle function in jQuery gives – and maybe even better slideToggle – also results in a display: none at the end, but before that a timing function of height which goes to zero.

if you like to have it more smooth:
( class to section that will be toggled: hidden-section ; button-class: toggle-button )

function toggle_on_click(){
?>
<script>
(function($){
	$(window).on('load', function(){
		$(".toggle-button a").each(function() {
			$(this).addClass('no-scroll');
			var target = $(this).attr('href');
			$(this).on("click", function(e) {
				$(target).slideToggle( 1000 );
				$(this).text(function(i, v){
					return v === 'Show' ? 'Hide' : 'Show'
				});
			});
		});
	});
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'toggle_on_click');

#top .hidden-section {
   display: none;
   min-height: unset;
}

You now can use the code above to open more than one section on that page! only the buttons target anchor must be correlated to the ID of the section.

see: https://webers-testseite.de/toggle-section/#toggle-section

btw: this slideToggle can have option ( f.e. instead of slow ( 400ms) you can insert 2000 for ms timing) : https://www.tutorialkart.com/jquery/?tutorial=jquery-slide-toggle

PS: the no-scroll class prevents the scrolling to that ID – if you like to have that maybe add a class to those buttons where the scrolling is not wanted – and then you only add that class to those buttons.

PPS: with or without that scrolling – there will be a “jump” in height ( same as on display: none) – you can not totally avoid that