第一個找到他文字的class 同樣寫css去改變文字顏色
第二個寫css 調整他的背景顏色

OBS Studio 官網提供的教學

Yes, what you want is indeed achievable. Open the browser source and
navigate to the Custom Css filed, clear everything in that field and use
the following css styles to style your prefered widget
/* To change the background and color in default theme */
.widget-1{
color: #000000;
background: transparent;
padding:1rem;
}

/* To change the background and color in gray theme */
.weather-frame .widget-2 .card {
color: #bfbfbf;
background: #1950a1;
}
/* To change the background and color of the badges inside gray theme to
fit your new background */
.weather-frame .widget-2 .card .row:last-child .weather-badge {
color: #bfbfbf;
background: #506179;
}