/*Apply to all mark tags*/
mark {
background-color: blue; /*Add your desired color*/
}
/*Apply it to a class*/
.mark {
background-color: blue; /*Add your desired color*/
}
/*Apply it to an ID*/
#mark {
background-color: blue; /*Add your desired color*/
}<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<p>Here is the <mark style="color: white; background-color:green"> searched query </mark> </p>
</body>
</html><body>
<p>The Math test is on <mark style="color: red;">Friday</mark>.</p>
</body><body>
<p>The Math test is on <mark>Friday</mark>.</p>
</body>