Does HDMI change colors on screen? | Xbox 360

This may seem like a no-brainer, but I was just wondering. I went over to my friends house the other day and while I was there I played his 360. I noticed that the colors on the home screen were darker. For example, the tiles on my 360 are a lighter green, while his were a regular or darker green. We have the same type of TV which is Sanyo, but he uses an HDMI cable and I don’t. I was wondering if the use of an HDMI would change the colors on the screen?

HD uses 10bit+ in some cases compared to normal 8 bit, but I think it was mostly due to his contrast settings.