JSFiddle - React, Tailwind, and code Playground

HTML

<input class="login_reg_input" value="click me">

CSS

input.login_reg_input {
    -ms-transition: background-color 1s;
    -o-transition: background-color 1s;
    -moz-transition: background-color 1s;
    -webkit-transition: background-color 1s;
    transition: background-color 1s;
}

input.login_reg_input:focus {
    background-color: #789;
}