Selecting elements with a certain background color

Question

if i understand the question correctly, the selector [attribute=value] will not work because <span> does not contain an attribute "background-color". you can test that out quickly to confirm it won't match anything:

$('#someDiv span[background-color]').size(); // returns 0

given:

.one, .two {
  background-color: black;
}

.three {
  background-color: red;
}

here's a snippet that will work:

$('div#someDiv span').filter(function() {
    var match = 'rgb(0, 0, 0)'; // match background-color: black
    /*
        true = keep this element in our wrapped set
        false = remove this element from our wrapped set
                                                         */
    return ( $(this).css('background-color') == match );

}).css('background-color', 'green'); // change background color of all black spans

.one, .two {
  background-color: black;
}

.three {
  background-color: red;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.0/jquery.min.js"></script>

<div id="someDiv">
    <span class="one">test one</span>
    <span class="two">test two</span>
    <span class="three">test three</span>
</div>

Javascript Approach

1. Get all spans
2. Convert spans nodelist to array
3. Filter spans array
4. Change the background color of matched span elements

// Get all spans
let spans = document.querySelectorAll('div#someDiv span'); 

// Convert spans nodeslist to array
spans = Array.from( spans ); 

// Filter spans array
// Get CSS properties object of selected element - [MDN](https://developer.mozilla.org/en-US/docs/Web/API/Window/getComputedStyle)
let arr = spans.filter( span => String( document.defaultView.getComputedStyle( span, null ).backgroundColor ) == 'rgb(0, 0, 0)' );

// Change background color of matched span elements
arr.forEach( span => {
    span.style.backgroundColor = 'green';
});

.one, .two {
  background-color: black;
}

.three {
  background-color: red;
}

<div id="someDiv">
    <span class="one">test one</span>
    <span class="two">test two</span>
    <span class="three">test three</span>
</div>