Add inline styles to head tag

gistfile1.txt

function customtheme_preprocess_html(&$variables) {
    $variables['#attached']['html_head'][] = [
        [
        '#type' => 'html_tag',
        '#tag' => 'style',
        '#value' => 'custom-class { background: red; }'
        ],
        'my-custom-theme'
    ];
}