The regraded screenshot is a little harsh on my eyes, but maybe I’m just too used to the grayish BD. I’m definitely interested in seeing more frames (or maybe even a whole clip) regraded to match the 70mm. You can find people all over the Internet who have posted images of the frames they acquired, so it shouldn’t be too hard for get a look at other 70mm frames for reference.
I just saw a 70mm showing last night. The colors in the regrade look correct to me. It had very strong blue-orange contrast, and not the green overtones of that BD frame posted. I couldn’t tell you about sharpness.