Custom styling for Bootstrap select
Check it out: https://developer.snapappointments.com/bootstrap-select/
You can change the color of the dropdown button through the different classes. And if you want another color, just override it in css. E.g.:
.btn {
background-color: #FFF;
}
You can overwrite the css styling by simply adding your own for example:
select {
background: #333333;
}
This is a very basic example but its just an example of how you can customize it to your own liking.