Change bg color in Shopping Cart (box)

[Guest]

I have "show shopping cart after product added" False in my admin.

But i would like the costumers to get attention to the Shopping Cart box after the product is added.

 

I guess some costumers dont understand that the product is added.

I want the Shopping Cart Box change from White bg color to red the first time a product is added.

 

So IF Shopping_cart = Empty then bg_color=white

Else

bg_color=red

 

How can i write this in PHP?

 

/Mange