JSFiddle - React, Tailwind, and code Playground

HTML

<div class="namecolorchange">
<center>
    <p style="color: #000; font-weight: bold; font-size: 15px;">Change name color</p>
    <input type="text" style="margin-bottom: 3px;" class="nameinput" name="nameinput"><span name="namedemo"></span>
    <input name="namebutton" type="submit" class="namebutton" value="">
</center>
</div>

JavaScript

$(document).ready(function() {
        $( "input[name='nameinput']" ).keyup(function() {
            var value = $( this ).val();
            
            $( "span[name='namedemo']" ).html( value.replace(/&1([\w]+)/, "<span style='color: blue'>$1</span>") );
            })
            .keyup();
        }
    );