Here are the current definitions of "race" according to the US census:
Here are the changes being considered for the 2020 census:
Here are some articles on the difficulty of categorizing Hispanics:
The Huffington Post
Pew Research Center
The New York Times
Here is another example of the difficulty of racial categories:
In The Latinos of Asia, Anthony Christian Ocampo shows that what "color" you are depends largely on your social context. Filipino Americans, for example, helped establish the Asian American movement and are classified by the U.S. Census as Asian. But the legacy of Spanish colonialism in the Philippines means that they share many cultural characteristics with Latinos, such as last names, religion, and language. Thus, Filipinos' "color"—their sense of connection with other racial groups—changes depending on their social context.