Yellow 1st down line in CFL

Question

How do they get the yellow 1st down line to go over the field but not over the players when they stand/run on it?

Answer 1

The magic of the CFL the best football in the world!

Answer 2

The line is designed to show as bright yellow on a green field of a specific shade.  When other colors are introduced to it, the computer knows that the colors are not the same shade as the field and doesn't display the line in that area.  I assume it can get a bit tricky with the Roughriders, but the other teams and all referees would pose no problem.