Christian Focus Publications have a very popular series of colouring books: Colour the Bible. This series of books apparently have just been printed in a well known Islamic country by one of the Bible Socities with the view of handing them out to 300,000 school children in that country. These colouring books are ideal for the slightly older child who is learning to write as there are words to fill in.
The Bible Heroes series by the same publisher is also better for older children as the colouring required is quite detailed.
The Learn About God colouring books however are ideally suited to a pre-school or early reader as the cartoon illustrations are simple and the fill in words not too complicated. These also accompany a full colour board book series.
I love the new set of colouring books CFP have done which take big words and the bible verses that use them. These books are great ways to familiarise children with the biblical use of words such as Creation and Holiness.