What are dark red calves?

"Dark red calves" could refer to a few things, so I need more context to give you a helpful answer. Please tell me:

* Are you talking about an animal? If so, what kind of animal?

* Are you asking about a specific breed of cattle? There are many breeds with red coloration.

* Are you asking about a health condition? Certain conditions can cause calves to have a dark red color.

Once you provide me with more information, I can give you a more accurate answer.