If there is a purpose to the choice I think selective colour photographs can be very effective, though it is something which can easily be overused. It is sometimes used to rescue an otherwise poor photograph by creating a focal point and it is rarely sucessful when used like this imho. 
I very much like it used in portraiture to express a mood and add atmosphere particularly when it is used with cross processing techniques. I like the work of Annabel Williams where she cross processes the film, but prints for skin tone. Resulting in skin tones that look natural in a world unnatural detached colour. 
 

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html