Sorry if this is old news and I missed an easy answer!!!
I have ProRes 422 HQ 1080p media and a matching timeline which was made from the media. When I switch between the viewer and canvass with the same clip there is a noticeable color shift. I have not rendered the timeline and see the difference on my 1080p monitor via a Kona 3g feed SDI.
What am I seeing??
Does the timeline REQUIRE a render? If so, you are seeing the fact that FCP, when it requires a render, displays a lower resolution image...even out to the monitor. When you render it..how does it look?
Wait, why do you need to render it? If the sequence settings match, then you shouldn't have to render. And if you need to render because you have a filter on it...well, that's why it looks different. Maybe.