Hi gloria
To align the depth to color camera you need to specify the stereoconfig:
stereo.config_stereo(align=color)
I also think 1080p is not supported on mono cameras, so they are set to 720p. You will need to downscale the color camera (ispScale 2/3).
If you wish to blend the streams together, i suggest you create a callback function for the visualizer in which you use the code from API version of RGB_depth_align.
Thanks,
Jaka