What does "Just black." mean in English for Spanish?

In English for Spanish, "Just black." means:

Solo.

Listen to "Just black.": (If you have an HTML5 enabled browser, you can listen to the native audio below)

This is a phrase that is used in the GamesForLanguage English for Spanish Language Game in the following scenes:

• English for Spanish 3, Level 1, Scene 1
• English for Spanish 3, Level 1, Scene 2