What advantages would there be to having a laser that can output the color white? I seen some videos on youtube that have 3 different lasers lined up with mirrors that combine the colors RGB to output white.

 

I do have an idea on how to make a single unit laser that can output the color white. I tried to search on the net if these white laser units already exist. If they do then I haven't come across it yet. Though I'm sure I'm not the only person to come up with the solution I am thinking about.

Nope, lasers will only produce one frequency of light, and so can't be white (which is a mixture of all colors).

Optical frequency combs output a discrete spectrum, but one that can cover all of the visible, so it ends up looking white.