Hi,
I'm assuming you use the code:
HTML Code:
<font color="#000000">Text to be coloured</font>
This is invalid code, as it is depreciated, but it will still work. Your website simply won't validate as XHTML 1.0 (Which vBulletin 3 is written in).
Alternatively, you can use this code:
HTML Code:
<span style="color: #000000">Text to be coloured</span>
It produces the same results, and it is XHTML valid. All the colours you wish to use will stay the same. You can still use words like black, yellow, orange, etc.
Hope this helps.