JSFiddle - React, Tailwind, and code Playground

HTML

<select name="Pcolor" id="image" style="height:30px;">
    <option value="">Избран цвят: Blue/Lt Blue </option>
    <option value="45751303" color-number="0">Black</option>
    <option value="45751343" color-number="1">Black/Pink</option>
    <option value="45751359" color-number="2">Blue/Lt Blue</option>
    <option value="45751324" color-number="3">Dk Purple/Purpl</option>
    <option value="45751390" color-number="4">Ink/Cerise</option>
</select>

JavaScript

var ColorSelectt = $('#image').find('option:contains("Black/Pink")').attr("color-number");
    alert(ColorSelectt);