Show form after youtube video ends
That looks doable by youtube-api.

What you can do is have the form loaded already when you should the color box, with display: none on form block.

Now with help of youtube api you can detect video end and can toggle visibility to display: block;

Refer here for youtube api example:- 

source https://stackoverflow.com/questions/7853904/how-to-detect-when-a-youtube-video-finishes-playing