IMO, the Google Camera App does produce a greenish tint on the M8, at least in the refocus mode after you refocused a little and let it render.
Already set the quality to high quality, but well, tinting is still there. Its not really heavy tinting, but enough to annoy me.
Normal photo mode seems fine so far, even tho it doesnt produce as good colors as the htc camera app.
Nevertheless, the new refocus tech is pretty logical and on still elements pretty powerful. I cant see it really useful for quick snaps or faster moving objects since it requires careful and steady movements.
Really hope that HTC improves the stock HTC camera app to let us adjust blur levels with increased accuracy on the captured image itself. the fail rate on ufocus sadly is pretty high still.
EDIT: I attached 2 images to show the green tint. First one is the shot right after i took it. second one is after refocusing. as you can see, there is a significant tint after processing. I even have the impression the processed image is now lower quality than before.