According to MovieWeb, Bumblebee is a modified 1967 Camaro SS in "Transformers 4." In the "Transformers" films directed by Michael Bay, Bumblebee has also been a classic 1977 Camaro and a 2008/2009 model based on the 2006 Camaro concept car.
The continuity of the film series indicates that Bumblebee utilized his technology to transform from his original 1977 Camaro form to the 2006 Camaro form. Bumblebee's original form as a car in the "Transformers" comic books was a yellow Volkswagen Beetle. The same is true of his car form in the animated series which was adapted from the earlier comic books.