How do I add a signature to my posts? I know it is in my preferences, but I thought it had to be as such:
<font face="verdana" size="1" align="center">
<p><b>

<font color="#FFBC81">S</font>
<font color="#81D1FF">t</font>
<font color="#00C083">a</font>
<font color="#A7C000">y</font>

<font color="#ECB7FF">S</font>
<font color="#FEAAC4">a</font>
<font color="#AEC7FE">f</font>
<font color="#FFCE81">e</font>

<font color="#FFADAD">&</font>

<font color="#81D1FF">G</font>
<font color="#94ECAB">o</font>
<font color="#ECB7FF">d</font>

<font color="#9AA55F">B</font>
<font color="#CAAB3E">l</font>
<font color="#51AAAF">e</font>
<font color="#F49CDA">s</font>
<font color="#CE9CF4">s</font>

<p><font color="#A4CFF0">~</font>
<font color="#FF9F9F">M</font>
<font color="#E3CBBB">a</font>
<font color="#DBCA3D">l</font>
<font color="#8DB7EB">a</font>
<font color="#9AA55F">c</font>
<font color="#E393FD">h</font>
<font color="#FEC2E0">i</font>

<font color="#81D1FF">T</font>
<font color="#8DB7EB">h</font>
<font color="#9AA55F">r</font>
<font color="#E393FD">e</font>
<font color="#FEC2E0">e</font>

<font color="#94ECAB">1</font>
<font color="#ECB7FF">0</font>
<font color="#A4CFF0">~</font>

</b>

</font>

Why isn't this showing up correctly as a signature in my posts?

because HTML is disabled on the forum, so that people can post codes without having them show up incorrectly.

in posts you can use vB code to change font colors and the like, but it is disabled in signatures.