You do this through something called styles. The best way to do this is through CSS (Cascading Style Sheets).
I would go through the entire tutorial of how to do it for you, but that might take a while, so I'll link you to a decent tutorial site for setting those attributes. You don't have to set up CSS to do it, you can also do it within HTML tags.
An example of how the code might look in HTML:
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<html>
<head>
<style>
a:link {text-decoration: none; color: #333300}
a:visited {text-decoration: none; color: #333300}
a:active {text-decoration: none;}
a:hover{text-decoration: underline; color:#000000}
body {
scrollbar-base-color: #999966;
scrollbar-arrow-color: #000000;
overflow: auto}
</style>
</head>
......
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http://www.w3schools.com/css/default.asp <--- This website does an excellent job explaining CSS and its attributes.