Hi Hadi,
You could change the colour by adding custom CSS within the admin area (Settings -> Company -> Customise HTML).
In the Header box, add the CSS below changing the colour codes to your desired colours.
CSS:
<style>
.cm-box-holder .customer-details .btn-light {
background-color: #c9cfd5;
border-color: #f8f9fa;
color: #212529;
}
</style>