:not() pseudo class

nagetive pseudo class:- :not()

HTML

<p class="hi">I am green now, but before this I was red (by first css rule color:red).</p>
<p>I am blue now, but before this I was green (by second css rule color: green), and before that I was red</p>
<p class="hello">I am blue now, but before this I was red (by first css  rule color:red).
    <span> <b>I am black because I am not span</b> I am red because I am not 'p' tag. before this I was blue (from parent 'p').</span>
</p>

CSS

p:not(.hi) {
    color: blue;
}