double border split color

<style>
#double {
border-top: 3.5px double #000;
border-left: 3.5px double #000;
border-right: 3.5px double #ccc;
border-bottom: 3.5px double #ccc;
}
</style>

<div id="double"><img src=https://www.rover.com/blog/wp-content/uploads/2019/06/cat-4223305_1920-300x200.jpg></div>