On Macs and iOS devices, in Safari, a element with a background color generates a gloss over itself. This does not seem to happen in other opera
Using -webkit-appearance:none; will remove also the arrows indicating that this is a dropdown.
See this snippet that makes it work across different browsers an adds custom arrows without including any image files:
select{
background: url(data:image/svg+xml;base64,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) no-repeat 95% 50%;
-moz-appearance: none;
-webkit-appearance: none;
appearance: none;
/* and then whatever styles you want*/
height: 30px;
width: 100px;
padding: 5px;
}