JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://www.phpied.com/files/rgbcolor/rgbcolor.js"></script>
<span id="blue">Hi there</span>
<br/><br/>
<span id="green">This is awesome</span>

CSS

#blue { color: blue; }

#green { color: yellow; background-color: #000; padding:3px; }

JavaScript

//set up color properties to iterate through
var colorProperties = ['color', 'background-color'];

//iterate through every element
$('*').each(function() {
    var color = null;

    for (var prop in colorProperties) {
        prop = colorProperties[prop];

        //if we can't find this property or it's null, continue
        if (!$(this).css(prop)) continue; 

        //create RGBColor object
        color = new RGBColor($(this).css(prop));

        if (color.ok) { 
            //good to go, let's build up this RGB baby!
            //subtract each color component from 255
            $(this).css(prop, 'rgb(' + (255 - color.r) + ', ' + (255 - color.g) + ', ' + (255 - color.b) + ')');
        }
        color = null; //some cleanup
    }
});