you can edit the error.tpl file in templates,look at the following html code

Code:
{/if}

{if $msg ne ""}

<table width="80%" align="center" bgcolor="#336699" cellpadding="6" cellspacing="3" border="0">
<tr>
<td align="center" bgcolor="#CCFFFF"><span class="success">{$msg}</span></td>
</tr>
</table>



{/if}

and change bgcolor color. if you want to mare modification in your font you can edit the style.css change the font color

ok
thanks