Module:Infobox/styles.css

/* Force light theme colors by default */
html:not([data-mw-theme="dark"]) .infobox {
    background-color: #f8f9fa;
    color: black;
    border: 1px solid #a2a9b1;
}

/* Dark mode for system preferences */
@media (prefers-color-scheme: dark) {
    html:not([data-mw-theme="light"]) .infobox {
        background-color: #1e1e1e;
        color: #f0f0f0;
        border-color: #444;
    }
}

/* Vector 2022 skin dark mode */
html[data-mw-theme="dark"] .infobox {
    background-color: #1e1e1e;
    color: #f0f0f0;
    border-color: #444;
}