Hi Pete,
Unfortunately, due to the nature of HDMI, both of what you are describing could be down other items in your setup.
Green/red sounds like something is muting the video - if this were that AVR600, you would get a black screen with a "HDCP failure" notice at the bottom. When you have this screen, can you get the OSD or menu of the AVR600 up? If not, the display is *likely* to be muting. If so, can you get the Oppo menu up? If not, then the Oppo is *likely* to be muting. Turning the Oppo on/off doesn't really point to any item in the chain as doing this causes the HDMI/HDCP authentication process to restart.
With regards to no audio with your V+ box, how do you have it connected and what do you have the "audio source" setting for that input set to? Having done a little research on this, I've found quite a few theads with people recommending HDMI connection for video & optical connection for audio (with some fiddling of the V+ HDMI override settings required). In this case, the AVR600 settings would be as per Sky boxes.
Regards,
Nick