If memory serves, Ponoko had templates, but dropped them.
Did find this article:
anything better?
Ah yes, this takes me back.
First, I am obligated to make reference to XKCD 927. I trust you know which one that is.
I don’t think there is a firm “standard” here. I believe the origin of this was the different colors you’d use to tell lasers such as Epilog and ULS whether to Cut, Engrave, etc… when you “printed” to them from Adobe Illustrator, CorelDraw, or other software.. So perhaps if we consult those resources, we may see some commonalities between them all, and perhaps Ponoko and most Makerspaces with lasers also had such processes, but I don’t know of any full on standard for this.
I suppose a reasonable next question is “what do you want to do?” because then the answer is “do whatever gets you there”. 
I want to make an example/sample/template file.
You are probably right that I was remembering the older printer-driver setups — as a starting point/initial example, one of those would work fine for my needs.
Working from the standard DXF colours I now have:
as a beginning point (punting on Light Gray, and will probably try not to use Yellow…) — now I just have to work out what the colours are used for by default.
One reference suggests:
- Red == cuts
- Black == engraving