umm i have a slight problem, any help would be absolutely great

the colour profiles on OS X dont seem to change the colour settings on my display, i can change it manually through my display but not through the System Preferences, why is this? i could do it on my old monitor, its just that i want Apple RGB colour profile and i cant seem to get it replicated manually

Thanks

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iMac ::: Mac OS X 10.6.1 ::: Intel Core2Duo 2.93GHz ::: NVIDIA Geforce GT 120 256MB ::: 4GB DDR3 RAM

Milanca Project ::: Mac OS X 10.6.1 Retail ::: Vanilla Kernel ::: Intel Core2Quad Q6600 2.4GHz ::: NVIDIA GeForce 8600 GT 256MB ::: 4GB DDR2 RAM ::: GIGABYTE GA-EP35C-DS3R