is_tax() conditional tag not working

Question

I have a menu item where a CSS class is added with a 'page_active' class (which visually shows an underline under the relevant item). This is added on certain menu items if the is_page('Latest') or is_archive('sites) conditions return true.

One of my main menu items (menu-item-3) is a custom taxonomy so instead of using either of the above two methods, I'm using is_tax('web') for a custom taxonomy called 'web'. This isn't adding the 'page_active' class though and also the CSS class is still being added to one of the other two items.

Below is the code - any ideas about how to solve this would be hugely appreciated.

CSS

.underline.page_active:after {
    content: '';
    position: absolute;
    width: 100%;
    height: 5px;
    background: #a882ff;
    left: 0;
    bottom: -0.39em;
    z-index: -1;
}

.menu-item-2.underline.page_active:after {
    width: 3.1rem;
    left: 5.7rem;
    z-index: -1;
    bottom: 2rem;
}   

HTML / PHP

<ul class="nav-menu-items">
    <li class="menu-item menu-item-1"><a class="td nav-link underline <?php if (is_page('Latest')) {echo "page_active";};?>" title="Latest" href="<?php echo esc_url(home_url( '/' ));?>">Latest</a></li>
    <li class="menu-item menu-item-2 underline <?php if (is_archive('sites') || is_tax('graphic-design')){echo "page_active";}; ?>">Design
        <ul class="submenu design-submenu">
            <li class="submenu-item submenu-item-1"><a title="Sites We Like" class="td nav-link" href="<?php echo esc_url(home_url('/sites'));?>">Sites We Like</a></li>
            <li class="submenu-item submenu-item-2"><a title="Graphic Design" class="td nav-link" href="<?php echo esc_url(home_url('/news_categories/graphic-design'));?>">Graphic Design</a></li>
        </ul>
    </li>
    <li class="menu-item menu-item-3"><a title="Web" class="td nav-link underline <?php if (is_tax('web')){echo "page_active";};?>" href="<?php echo esc_url(home_url('/news_categories/web'));?>">Web</a></li>
    <li class="menu-item menu-item-4"><a title="Marketing" class="td nav-link underline" href="<?php echo esc_url(home_url('/news_categories/marketing'));?>">Marketing</a></li>
</ul>

Answer 1

I found the solution to this, the is_tax(); method needs two arguments - the taxonomy and the term itself, so it should have been:

is_tax('news_categories', 'web')

Just as an extra point the is_archive('sites') should also have been is_post_type_archive('sites')