The sire can't be pure poodle if he's a merle. Poodles don't carry the gene for merle, so the merle gene has to be brought into the gene pool by another dog. Cockers though can be merle, so a merle cockapoo (from the moms side) isn't uncommon.
Many sites that have merle poodles will swear up and down that "Poodles do come in the Merle Coat Pattern! Studies have been conducted and it has been proven that Poodles do infact carry the Merle Gene." But (oddly enough) they can never seem to pull up these studies. I can guess why.

Often people will pull in another breed, like a pom or a small aussie, that is, or carries, merle. Then the pups can be bred back to poodles, and after enough gens, the resulting dogs can appear as full poodle. But it is not.
Here as some obvious mixes being advertised as 'pure bred poodles'. :argh:
This pup has a insanely block-y muzzle
http://www.utopiapoodles.com/FancyMerles/shal_fancy.jpg
This dog is very long (poodles should be square)
http://www.mysticalmerles.com/inside/images/stories/poodlemoms/img_0614.jpg
Another block muzzle
http://www.poodlepleasure.com/merlin.jpg
The worst coat I've seen in years for a 'pure poodle'
http://www.mysticalmerles.com/inside/images/stories/100_7531.jpg
Too high of ears (should be level with the eye) and a very low set tail
http://photos.worldpetmarket.com/859/pet_859_3.jpg
Now don't think I'm bashing the color. I think they're insanely adorable. I love merles, and I love poodles. I'd love a merle poodle!

My beef is with dogs that are not tested, not show, not trialed, obviously ill bred, yet being advertised as 'pure merle poodles' and totted as the greatest think
evers!!1. Serious pet peeve of mine.
Outcrossing for traits isn't too common, but it can work great. There are Boxers with natural bob tails from letting one and only one naturally bob tailed corgi into the lines long ago, and now you can't even tell. And dalmatian breeders let in a pointer once, to fix there gallstone problem. It worked!
But this is not line crossing a amazing poodle with a amazing merled dog, just to grab the color, then breeding true again tell the resulting dogs are show quality again (fur type and body) yet merle. This is finding a new fab to exploit.
Oh man that got huge. :XD: Sorry. Hope it helped someone at least...