How to check color font in php for checking data form

[jerc]

Q: How to check color font in php for checking data form

This is what I did in my php but the color is in black

if(isset($_POST['email']))
{
 $email=$_POST['email'];
 
 $checkdata=" SELECT email FROM registration WHERE email='$email' ";
 
 $query=mysqli_query($db,$checkdata);
 if(mysqli_num_rows($query)>0){
 
  echo "Email Already registered";
 }
 else
 {
  echo "AVAILABLE";
 }
exit();
}