A Nurse's Education Includes Physiology

http://scienceblogs.com/scientificactivist/2008/04/why_are_veins_blue.php

http://www.enotes.com/nursing-encyclopedia/blood-gases

And since it's now clear the material in the above pages is too complicated for Laurie Meegan LPN, I've found something written especially for elementary children. Note Mr. D's very first instruction:

Blood is never blue.

http://www.globalclassroom.org/blublud.html

http://www.imt.liu.se/edu/courses/TBMT36/pdf/blue.pdf