You can’t manually input colors because all color fields has read-only attribute.
You can remove these attribute in file imdbinfobox.php in line number 125, 129, 133 and 137
find this
<tr>
<td><strong>Heading Background Color</strong></td>
<td><input class="color" value="<? echo get_option('imdbheadbg'); ?>" name="imdbheadbg" readonly="readonly" /></td>
</tr>
<tr>
<td><strong>Heading Text Color</strong></td>
<td><input class="color" value="<? echo get_option('imdbheadfg'); ?>" name="imdbheadfg" readonly="readonly" /></td>
</tr>
<tr>
<td><strong>Body Background Color</strong></td>
<td><input class="color" value="<? echo get_option('imdbbodybg'); ?>" name="imdbbodybg" readonly="readonly" /></td>
</tr>
<tr>
<td><strong>Body Text Color</strong></td>
<td><input class="color" value="<? echo get_option('imdbbodyfg'); ?>" name="imdbbodyfg" readonly="readonly" /></td>
</tr>
and replace with
<tr>
<td><strong>Heading Background Color</strong></td>
<td><input class="color" value="<? echo get_option('imdbheadbg'); ?>" name="imdbheadbg" /></td>
</tr>
<tr>
<td><strong>Heading Text Color</strong></td>
<td><input class="color" value="<? echo get_option('imdbheadfg'); ?>" name="imdbheadfg" /></td>
</tr>
<tr>
<td><strong>Body Background Color</strong></td>
<td><input class="color" value="<? echo get_option('imdbbodybg'); ?>" name="imdbbodybg" /></td>
</tr>
<tr>
<td><strong>Body Text Color</strong></td>
<td><input class="color" value="<? echo get_option('imdbbodyfg'); ?>" name="imdbbodyfg" /></td>
</tr>