Product Colour Attribute
This defines the colour of the item, Google accepts up to 10 colours per item in the Joomla Google Base Component.

This means you can have 1 product but in 10 colours, such as 

Iphone4 Phone Covers
- White
- Black
- Green

Before this you would have had to put in 3 products and google would have failed 2 of them as duplicate items. Now you only have to input 1 item with the 3 colours. This also works with the sizes attributes, meaning 1 item can have multiple sizes and multiple colours, allowing you to merge many items into one with multiple attributes.

There is more information on Googles Help Pages

Have you noticed how the word "color" is spelt wrong in the attribute, that's because Americans cant spell