input field color border css code example
Example 1: change input border color when selected
input:focus {
outline: none;
border: 1px solid red;
}
Example 2: how to change input border color with js
document.getElementById("fName").className = document.getElementById("fName").className + " error"; // this adds the error class
document.getElementById("fName").className = document.getElementById("fName").className.replace(" error", ""); // this removes the error class