If anyone else wants to accomplish something similar, I just figured it out.
The extra field number needed to be used in "if"statement as well.
This code works -
Code:
{section name=brand}
{if $extra_fields[6].active eq "Y" && $extra_fields[6].field_value}
<strong>{$extra_fields[6].field}:</strong> {$extra_fields[6].field_value}
<br>
{/if}
{/section}