He hecho una caja de selector y quiero cambiar el borde y el botón.

Mejor dicho quitar el borde.

Pego HTML Y CSS:

#lenguajes {
position: absolute;
float: left;
right: 0px;
top: 2px;
}

#sr_language_menu_select {
background-color:#003366;
font-family: "Arial";
font-size:11px;
font-weight:400;
text-transform:uppercase;
}

.tx-srlanguagemenu-pi1 {

}

.sr_language_menu_form {

}

fieldset {
color:#0066CC;
border: none;
}

legend {
display:none;
}

label {
display:none;
}

HTML:

<div id="lenguajes">
<!-- CONTENT ELEMENT, uid:83/sr_language_menu_pi1 [begin] -->
<a id="c83"></a>
<div class="tx-srlanguagemenu-pi1">

<form action="" id="sr_language_menu_form">
<fieldset>
<legend>Spanish</legend>
<label for="sr_language_menu_select">Spanish</label>
<select size="1" name="L" title="Spanish" onchange="if (this.options[this.selectedIndex].value == '') return;if(false || this.options[this.selectedIndex].value != '0') { top.location.replace('index.php?id=20&amp;no_cache=1&amp;L=' + this.options[this.selectedIndex].value ); } else { top.location.replace('index.php?id=20&amp;no_cache=1'); }" id="sr_language_menu_select">
<option value ="">Spanish</option><option value ="">----------</option><option value="0" class="tx-srlanguagemenu-pi1-option-0">English</option>
</select>

</fieldset>
</form>

</div>

</div>