I have the same display issue with my Macbook Pro 3.1 (mid 2007), 2.4 Ghz, A1226, 15.4 " display
The color changes intermittently as you described. I have connected to the external monitor the picture seems perfect.
Can anyone suggest where the problem persist?
Should I need to replace LCD or only the Lcd cable?
It appears the motherboard or the GPU is ok as the external monitor is fine.
Backlighting problem is also cannot be as the internal display is bright when it works normal, so power inverter is working fine I presume.
Need to check the LCD display cable
Also, can it be due to software problem or a RAM problem, as I upgraded my OS from 10.5 to 10.6.3 leopard and Ram was increase to 4Gb from 2GB.