OK here's a weird one. I have an avalanche, but it's the same system so figure I'd try here. I've been wanting to utilize the rear entertainment drop down for a while now. Finally decided to get an hdmi to rca converter and use a chromecast to stream things on it. While it does work pretty well, the front screen remains in black and white. Weirdly when I pull the hdmi out real quick and put it back into the rca cables, it flashes color bars before switching to the gray bars then displaying the chromecast. The drop down is in full color. I tried messing with the settings on the cast but nothing changes anything. This seems to be more of a system thing than anything. Everything is connected properly, separate power to the converter and the chromecast as well so thays not an issue
