Lee,
In a perfect world, or even just a reasonable one, I agree you would expect the same colours on the same computer
Here are some useful links if you want to check if an app is doing colour management correctly:
http://petapixel.com/assets/uploads/2012/06/S2fzq.jpg - if the car is purple then colour management is broken
http://www.color.org/version4html.xalter - also checks for v4 ICC profile support
Unfortunately, this stuff is often hard to get right... and even if you do it won't help if somebody is looking at your image on a browser without colour management and an unprofiled CRT screen
Cheers,
Rick.