You can use the adjacent sibling combinator:
header+p {
color: red;
}
<section>
<header>
<h2 class="licht"><span id="Standort" class="-sitemap-select-item-selected">Standort</span></h2>
</header>
<p>Lorem ipsum</p>
</section>
If you only can base yourself on the ID of a child element contained in the header
, there's no pure CSS solution, and you'd have to rely on JavaScript:
document.getElementById('Standort')
.closest('header')
.nextElementSibling
.style.color = 'red';
<section>
<header>
<h2 class="licht"><span id="Standort" class="-sitemap-select-item-selected">Standort</span></h2>
</header>
<p>Lorem ipsum</p>
</section>