Expanding the allowed HTML tags in comments?

I have no problem doing this in a comment, as an administrator:

<b>bold test</b> <i>italics test</i>
<u>underline test</u> <font
color="#ff9900"> color test</font>

But the subscribers can’t underline, add color to words nor add images.

Is it that only the admin can use more HTML tags than those suggested under the comment form?

<a href="" title=""> <abbr title="">
<acronym title=""> <b> <blockquote
cite=""> <cite> <code> <del
datetime=""> <em> <i> <q cite="">
<strike> <strong>

How to enable the subscribers to add color to text, and add images?

The tags that are allowed in comments are stored in the $allowedtags global variable. You can try adding elements to that list (the key is the tag name, the value is an array of allowed attributes). If you have problems with the timing you can play with the CUSTOM_TAGS global variable.