[SOLVED]How to make a new design for checkout button 1.5.6.4

hi, my version is 1.5.6.4 and i want to make a little change of checkout button. want to make a red background with white color of text. this custom change need to be only for checkout button. i try to make my self, but all links in that div tag are in one css rule and have not success. can someone tell me or suggest me a solution for my request. here is and jpg for more clearance. thank for help before.
edit stylesheet.css from default template folder. FOUND THIS CODE at line 299:
#header .links {
position: absolute;
right: 0px;
bottom: 3px;
font-size: 10px;
padding-right: 10px;
}
#header .links a {
float: left;
display: block;
padding: 0px 0px 0px 7px;
color: #38B0E3;
text-decoration: none;
font-size: 12px;
}
#header .links a + a {
margin-left: 8px;
border-left: 1px solid #CCC;
}
HERE ADD : whitout this line
#header .links a + a + a {
margin-left: 8px;
border-left: 1px solid #000;
}

#header .links a + a + a + a{
color: #ffffff;
background: #ff0000;
margin-left: 8px;
border-left: 1px solid #000;
}

explanation : #header .links a + a { }group is for the second link
#header .links a + a + a { } group is for the third link
#header .links a + a + a + a { } is for the forth link
they are indipandents each other groups. any design for group not effect others