I've found it very strange then...with all the application photoshop, office, any image editor and so on I can edit change or do whatever with an image. The printer prints the graphic perfectly.
However only and **only with**with the iWork applications I get those problems. I may do whatever I want with the images. The printer will print them correctly. The only time when the problems begin is when you add some shadow or/and transparency. Those basic editor tools are also available in other application which cause no problems at all. It's only iWork that has those problems.
Test for yourself and I really hope you do:
Start Pages and choose an empty page layout
Insert any graphic you want
Add a shadow to the graphic
Print the document
Are the colors the same on the paper and on the screen?
I've tested this with: HP 1210, 140, 970Cxi, 890C, 5500 All give the same results.
If others has not trouble at all I'm really interested in which printer they use.