Thanks Michelle didn't know Donald had already covered that one. It is the same as link I posted to Greg Gormans site. As you say lots of ways to do it - I don't use b/w much only experimented a bit little while ago and found the channel mixer easy and quick to do - but those with more serious interest would no doubt want to move onto the more advanced way to achieve better results.

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