Contact button color

Hi,

First, you should NOT change the CSS code in the file hikashop.css.
Next time you update HikaShop, you'll lose your changes.
Instead, you should write CSS code to override the default CSS and add it to your Joomla template.
Most templates have a mechanism to add custom CSS.
I checked your website and it seems that you're using a template based on the Astroid framework. So this should be how to add custom CSS on your website:
docs.astroidframe.work/custom-code/custom-css
Just copy / pasting the CSS from hikashop.css there and modifying it should do it.
The fact that no change occurred when you changed the CSS of hikashop.css is because of your template. It has a caching mechanism for the CSS. So, unless you clear the template's cache, you won't see a change. You can see on the Astroid documentation page above that it recommend clearing the cache of the template after adding your custom CSS code.

However, just copy / pasting the CSS code is a crude way to go about it and won't allow you to segregate elements with the same class in different areas like you want to do.
Instead of just copy / pasting the CSS code, you can use the inspector tool of your browser to study how the HTML elements are on the area you want to change.
So, if you check the HTML of your contact button, you'll see this:

<div id="hikashop_product_contact_main" class="hikashop_product_contact_main">
   <a class="hikabtn" rel="nofollow" href="/nuestros-productos/maquinas-y-equipos-de-aseo/apiradoras/product/contact/cid-169">
       <span>
           <i class="fa-solid fa-comment"></i>
           <font color="green">Consulta por este producto</font>
       </span>
    </a> 
</div>

.hikashop_product_contact_main .hikabtn{
  bakground-color : #eaedf0 !important;
}