Changing the color of the Topmenu background

I think its a bug in the template.
Since in the demo on your site the links to the brands aren't shown and when i look at the demo installation provided when i bought the template. it gives the same error + shows all categories with the brands products underneath.

Warning: array_merge() [function.array-merge]: Argument #2 is not an array in C:\xampp\htdocs\maximumhealth\templates\hot_ecommerce\html\com_virtuemart\category\default.php on line 45

Warning: Invalid argument supplied for foreach() in C:\xampp\htdocs\maximumhealth\libraries\joomla\html\html\select.php on line 536

The categories shown when you select a brand's item was related to a setting in VM/Configuration/templates "show subcategories"
The error code remains, but this can be shut off by disabling error codes. I do still wonder if the error slows down the shop or can cause any other inconvenience

It will not cause any problems. Some further VM version will probably solve error message.