Well that wouldn't be me then . The color moiré that you see is the product of the regular sensel grid and the laser engraved pattern of the focus screen. Apparently they are both repetitive, but at different spatial frequencies, hence the moiré. You'l see similar effects between the sensel grid and the LCD on the camera, but they are all depending on a certain level of detail magnification, so it's hard to predict how it's going to look, or even if it shows.
That's probably all quite true, Bart. No dispute there. One has to be at a certain distance from a target in relation to a certain size of repetitive detail, and such distance should also be in accordance with the focal length (or magnification) of the lens, so a bit of experimentation is required in order to see the effect.
However, such color moire and circular artifacts around straight B&W lines on a test chart are also apparent through an optical viewfinder when, presumably, the sensel grid is not involved.
This was the method I used in the old days when my main camera was the Canon 20D, which doesn't have autofocus fine tuning, and when I used to buy lenses from 'bricks & mortar' camera stores and was worried about QC variation and pleased that I could easily return a lens without questions asked, within a week of purchase.
Being aware of differences between artificial and natural, real-world scenes, I constructed a test target for my purposes designed as a mixture of real-world and artificial products. The test target, pictured below, consists of a mixture of Norman Koren B&W line test charts, various real-world textures such as old sandpaper, patches of fabric, bunches of twine, all against a background of the texture of natural timber. I even included a few neutral-grey patches.
I admit it's not a pretty sight to behold, but it served its purpose.
Concerned now, that what I recall seeing a few years ago was merely a peculiarity of the Canon 20D, I retrieved that dusty, old test target from the garden shed, and hung it on the screen-door-latch of my new house.
I used manual focus with my D7000 and Nikkor 24-120/F4 zoom lens, set at 31mm and F5.6.
This was a quick and dirty shot. No tripod. As you can see, I didn't even crouch down far enough to get the door frame vertical. The point is, this shot was taken when I saw the maximum degree of circular artifacts on the artificial part of the test target. The degree of moire was not as great as I recall seeing several years ago, but that is probably due to the fading of the dye-based test target prints, printed on my Epson 1290 as I recall. If anyone reading this post wishes to try this procedure for accurate autofocussing, I'd recommend printing the line chart on premium gloss, or semi-gloss paper, and placing it in bright light outside.