Video in gray, why?

edit

The idea is to perform some computation on an image source that is a bit more robust and invariant to lighting changes. In order to do so they are converted to greyscale images and a histogram equilization is applied. Also using grayscale images ensures you only need computations on a single channel, not on the three color channels which increases processing time.

Thanks Stevens you are awesome. Apparently this forum has prepotent people that don't like newbie questions. They want everyone to know everything but fortunately people like you exist. Thanks.

Don't take the -1 too hard. I sometimes see questions like this and also think that the topic starter didnt put effort in finding the solution. However then I remember I was an OpenCV noob once too. Good luck!