Replacing Specific color code in css using jquery

you might consider changing it with jquery.

$(function() {
  $('.awesome-one').hover( function(){
     $(this).css('background-color', '#789034');
  },
  function(){
     $(this).css('background-color', '#456780');
  });
});

You might want to try the following:

Put your stylesheet inline into the document, wrapped by a style tag:

<style id="myStyles" type="text/css"> /* all your css here */ </style>

Now you can probably get all the contents of this via

var myCss = $("#myStyles").text();

Then go ahead and do the replacement magic:

myCSS = myCSS.replace("#789034", "#456780");

And in a last, hopeful effort, put it back in the DOM:

$("#myStyles").text(myCss);

But even if this should work, it seems to me very probable that you are bringing an XY problem.

Why, its elementary, dear Watson. Just grab all possible style-keys, check if they contain the word color, convert them from camel case to hyphenated, then replace all occurrences of the color with the new one using a complex regex system. DUH!

...I have too much free time, sorry:

var keys = Object.keys($('html').get(0).style);
var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec('#789034');
var rgb = 'rgb(' + parseInt(result[1], 16) + ', ' + parseInt(result[2], 16) + ', ' + parseInt(result[3], 16) + ')';
for (var k in keys) {
    key = keys[k].replace(/([a-z])([A-Z])/g, '$1-$2').toLowerCase();
    if (key.indexOf('color') > -1) {
        $("*").each(function () {
            if ($(this).css(key) == rgb) {
                $(this).css(key, '#456780');
            }
        });
    }
}

div {
    height: 50px;
    width: 50px;
}
.common-color {
    color:#789034;
}
.new-cls {
    border-style: solid;
    border-color:#789034;
}
.awesome-one {
    background-color:#789034;
    height:200px;
    width:300px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="common-color">hello</div>
<p class="new-cls">cool</p>
<div class="awesome-one"></div>

EDIT:

Or, if you would rather, here is a simple function to use. Color 1 will be replaced by color 2:

function replaceColor(color1, color2) {
    var keys = Object.keys($('html').get(0).style);
    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(color1);
    var rgb = 'rgb(' + parseInt(result[1], 16) + ', ' + parseInt(result[2], 16) + ', ' + parseInt(result[3], 16) + ')';
    for (var k in keys) {
        key = keys[k].replace(/([a-z])([A-Z])/g, '$1-$2').toLowerCase();
        if (key.indexOf('color') > -1) {
            $("*").each(function () {
                if ($(this).css(key) == rgb) {
                    $(this).css(key, color2);
                }
            });
        }
    }
}