Yellow Pages!

 Yellow Pages refers to a telephone directory of businesses, categorized according to the product or service provided. As the name suggests, such directories were originally printed on yellow paper, as opposed to white pages for non-commercial listings. The traditional term Yellow Pages is now also applied to online directories of businesses.
The name and concept of "Yellow Pages" came about in 1883, when a printer in Cheyenne, Wyoming working on a regular telephone directory ran out of white paper and used yellow paper instead. In 1886 Reuben H. Donnelley created the first official yellow pages directory, inventing an industry.

Today, the expression Yellow Pages is used globally, in both English-speaking and non-English speaking countries. In the United States, it refers to the category, while in some other countries it is a registered name and therefore a proper noun. The term Yellow Pages is not a registered name within the United States and is freely used by many companies.

In Belgium, the Republic of Ireland, Israel, the Netherlands, and Romania the 'Yellow Pages' are known as the Golden Pages.