By default the Astra Pro camera does not stream RGB image along with depth.
In order to get both images streamed, use the following packages.

git clone https://github.com/tonybaltovski/ros_astra_launch.git --branch upstream
git clone https://github.com/tonybaltovski/ros_astra_camera.git --branch upstream
cd ..
rosdep install --from-paths src --ignore-src --rosdistro=indigo -y
catkin_make
source devel/setup.bash
rosrun astra_camera create_udev_rules
(you may need to reboot here)
roslaunch astra_launch astra_pro.launch

Good luck!