zoneminder/web/skins/classic/css/base/views/monitor.css

.swatch {
    border: 1px solid black;
    margin-left: 3px;
    padding: 0px;
}

.SourceOptions input,
.SourcePath input {
  width: 100%;
}

input[name="newMonitor[Width]"],
input[name="newMonitor[Height]"] {
  width: 80px;
}