JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<head>
<link href="https://cdn.jsdelivr.net/npm/select2@4.1.0-rc.0/dist/css/select2.min.css" rel="stylesheet" />
<script src="https://cdn.jsdelivr.net/npm/select2@4.1.0-rc.0/dist/js/select2.min.js"></script>
</head>
<body>


<select class="js-example-basic-single" name="state">
  <option value="1">Select Item 01</option>
  <option value="2">Select Item 02</option>
  <option value="3">Select Item 03</option>
  <option value="4">Select Item 04</option>
  <option value="5">Select Item 05</option>
  <option value="6">Select Item 06</option>
  <option value="7">Select Item 07</option>
  <option value="8">Select Item 08</option>  
</select>


</body>
</html>

CSS

:root {
    --Color1: #3333FF;
    --Color2: #FFFFFF;
    --Color3: #EC2121;
    --Color4: #000000;
    --Color5: #AAAAAA;
    --Color6: #F99320;
}

.js-example-basic-single {
  width: 200px;
}

/* Search Box */
.select2-container--default .select2-search--dropdown .select2-search__field {
  background: var(--Color4);
  color: var(--Color2) !important;  
}
/* Search Box border */
.select2-search--dropdown{
  background: var(--Color6);
}
/* Selected / Initial state input */
.select2-container--default .select2-selection--single .select2-selection__rendered {
  background: var(--Color1);
  color: var(--Color2) !important;  
}
/* Option List Area */
.select2-results__option {
  background: var(--Color1);
  color: var(--Color2) !important;   
}
/* Arrow button */
.select2-container--default .select2-selection--single .select2-selection__arrow {
  background: var(--Color3);
}

/* Selectable items highlight */
.select2-container--default .select2-results__option--highlighted.select2-results__option--selectable {
  background: var(--Color3) !important;  
}

/* Selected item highlight */
.select2-container--default .select2-results__option--selected {
  background: var(--Color5) !important; 
  color: var(--color4) !important;
}

/* Search result message area */
.select2-results__message {
  background: var(--Color6);  
}

JavaScript

$('.js-example-basic-single').select2({
  placeholder: 'Select an option'
});