Hi, is it possible to highlight an option in a dropdown box?

Code:
<td style="text-align:right;">Class:</td>
	<td><select id="class" name="class" onchange="cl(this,cl11,cl12,cl13,cl14,cl15,cl16,cl21,cl22,cl23,cl24,cl25,cl26,clp)">
		<option value="">Choose one</option>
		<option value="0">0</option>
				<option value="1">1</option>
				<option value="3">3</option>
		<option value="4">4</option>
		<option value="5">5</option>
	    <option value="6">6</option>
			</select></td>
I want to highlight the options 1 and 4, but how do I do this?