<style>
    {% assign categories = page.categories %}
    {% assign category = site.data.categories[categories.first] %}

    code {
        color: {{ category.backColor }};
    }

    pre {
        color: {{ category.backColor }}
    }

    ::selection {
        background-color: {{ category.backColor }};
        color: {{ category.textColor }}
    }
</style>