Selective color is used to draw a viewers eye to a part of an image you feel is important for the viewer to look at.
Do you think it's important that the viewer's eye be drawn to the hot coal at the end of the cigarette?
I personally don't FULLY agree with this. I've seen plenty of pictures of toddlers with say a bright red umbrella. The entire shot is B/W apart from the umbrella. I like pictures like that.
The point isn't to draw your focus to the umbrella. On the other hand, the same set up with a cat and the eyes are coloured is most certainly there to draw in your attention.
I like this picture. Is the cigarette body coloured too? I would grey scale it if so.