In the blu-ray or display settings on your XMB, there is a toggle for a color-related setting. I don't remember exactly what it is called, but its two settings are I think "limited" and "full." The default is limited, because not all TV's can handle full. Try to switch it to "full" and see if it will work. If your TV can handle it, all the light pollution in dark scenes will disappear. When I first noticed it and switched it on, it was like I had a whole new TV, it makes a big difference.
If the light scenes are working, it's not likely the HDMI cable. Don't waste any more money on expensive HDMI cables.
OK, here it is: RGB full range, in the display settings.
You should also check video output format in the BD settings, for HDMI there are two choices, RGB and Y/Pb/Pr (component-type). It depends on the TV. If it's set to automatic, it should auto-detect and work, you could trial and error setting it to both settings too.
The other setting that might matter is super-white, if your TV has it. In the display settings.