Hough Transform example: Result of cvtColor()

I am learning to implement Hough transform and I have [this](http://docs.opencv.org/2.4/doc/tutorials/imgproc/imgtrans/hough_lines/hough_lines.html) example program from OpenCV documentation. It contains the following two lines of code: Canny(src,dst,50,200,3); cvtColor(dst,cdst, CV_GRAY2BGR); I tried displaying both `dst` and `cdst`. Both these images look the same. So, I wonder why `cvtColor` is applied? Is `cdst` created for the sole purpose of displaying lines detected in `dst`?