Customizing UI, change highlight color of each select in the UI

[fleggio1970]

Hi,
my need is to change highlight color for each select element from green to gray. I m really stuck after trying different css options:
.swagger-ui .response-control-media-type--accept-controller select:focus{
background-color: #f7f7f7;
}
.swagger-ui .response-control-media-type--accept-controller select:checked{
background-color: #f7f7f7;
}
.swagger-ui .response-control-media-type--accept-controller select:selection{
background-color: #f7f7f7;
}
.swagger-ui .response-control-media-type--accept-controller select:hover{
background-color: #f7f7f7;
}
.swagger-ui .response-control-media-type--accept-controller select option:hover{
box-shadow: 0 0 10px 10px #e1358f inset;
}

Is there anyone who can help me and suggest the right way to change it via css? Shall i make changes to swagger-ui-standalone-preset.js?

Hereyby a screenshot of what i need to change: