Do you say 'white blackboard'?

English is not my first language, so I'm not sure what you commonly call one of these:

I'm trying to choose between blackboard, white blackboard, or maybe just 'slate'.

That is quite simply a whiteboard.

Blackboard can be defined as:

A smooth, hard, dark-colored panel for writing on with chalk.

Whiteboard can be defined as:

A panel covered with white, glossy plastic for writing on with erasable markers.

I most often hear these referred to as dry erase boards.

That is, quite naturally, called whiteboard, Bierce does not have an entry for the word but it would probably be:

• the writing board that always get written on with permanent marker

I refer to it as simply a whiteboard.