ffmpeg Color Correction: Gamma, Brightness and Saturation
These settings helped me to lighten up a dark video using the filter eq, with some added saturation.
Syntax:

filtername=option1=value1:option2=value2:option3=value3... These can be in any order.

Filter ranges and all options:
https://ffmpeg.org/ffmpeg-filters.html#eq
Preview:
ffplay -vf eq=brightness=0.06:saturation=2 INPUT.MOV
Render:
ffmpeg -i INPUT.MOV -vf eq=brightness=0.06:saturation=2 -c:a copy OUTPUT.MOV 

Alternative filters: curves and pp.