According to this, TechDraw currently does not support colored exports. I'm creating this post for further searches.
While creating a laser cut output by using a unfold sketch of a bent sheet metal, it's important to set the bending lines to different colors, and also different colors for laser marking (if there is any) etc. These are set properly in 3D design but when I create the projection, they are not kept as is.
Reported here: https://www.freecadweb.org/tracker/view.php?id=3603