It's to do with the computer - namely, the graphics card. It's possible one is viewing it with 16million colours, the other with only 256. 256 is sure to show you a set of diminishing bands, instead of a smooth gradient.
Definition: Computer rage is a heightened physiological response with associated feelings of anger and frustration resulting from using a computer or other complex electronic device. It may result in the physical assault of the computer or similar item. Computer use often leads to verbal abuse and occasionally physical violence towards the object. Computer rage may be caused by distress due to a hardware or software problem which the enraged person is unable to correct.