can i write a code? if yes, which is the language?
You can use batch scripting or sequencer: RealityCapture Help, https://www.youtube.com/watch?v=cZv_DKQMSVg
I noticed that when the alignment finishes, it performs a color correction. Why is that?
You need to have set that in the Color and Texture settings:
I have three sets: the first set is a nadir drone mission georeferenced using GCPs, a set of photos taken with a drone and therefore with GPS position, and a laser scanner set georeferenced in another program using the same GCP coordinates. Now, I want to merge them into one set. What do you recommend I do?
I suppose you asked this more times before. Jakub described the process above, the process was also described here: georeferencing and registration a component - #6 by OndrejTrhan.
If all your datasets are georeferenced, you can import the components into new project and then use the option Merge georeferenced components in the Alignment settings.
Just drone images could have not so precise GPS, so I would use the GCPs also there.