Both Harrison's and Clawson's books both state that the finish ona 1911A1 frame and the slide should be the same. Either both parked or both blued.
I can find nothing that states that the shade of the finish should be the same.
Question:
Can a 1911A1 be correct if both slide and frame are parked and the shade of each is somewhat different?

From p. 103 in Clawson's Collector's Guide dealing with original finish:
"The receiver and slide must always be the same color (shade, sheen, etc.) whether blued or parkerized."
That said, there are exceptions to the rule. There are some slight differences in some cases. Remington Rand pistols in some serial ranges often are slightly mismatched in color.
Some very late 1945 Ithaca pistols have darker slides than frames. Some late 1944-early 1945 Colt pistols have slides that appear darker and smoother than frames.
I believe there were some cases where slides and frames were manufactured at different times over a period of time when manufacturing processes and/or finishes changed slightly, which led to slightly mismatched finishes in some cases.
The way the surfaces were prepared for finish played a major role in what the finish would actually look like. The same finish can be applied and look somewhat different on surfaces prepared in slightly different methods.
Remington Rand's color got lighter all during 1945. There are at least three shades of finish on their pistols in 1945 alone. I'm confident they probably didn't use three different finishes, and that the change in shade is due to surface preparation being different. Even the amount of sandblasting done prior to finish can substantially change the color of the finish.
Also, many slide and frame combos will appear the exact same color at one angle, but may look different at other angles. Wear and aging can even effect the color or shade of the finish. Slides will often appear different due to holster wear and/or contact.
So...yes, to a point finishes may vary a little. But there are plently of known examples in most serial ranges to compare finishes on. Each manufacturer's finish and surface prep was a little different and are usually identifiable.
Singers and US&S pistols normally display pretty consistently the same colors frame and slide, except in cases of slide wear and aging.
On Rem Rand and Ithaca pistols that seem to have finishes that vary a little, look at the wear patterns and P proofs to verify originality. Look for other signs of mismatching. Look at other known examples for comparison.
On Colt pistols, the P proofs do not necessarily have to match. But slide legends, sights, wear patterns, numbered slides (where they apply), etc., can all help to verify originality in most cases.

Thanks for this. The sentence on the angles sure calls it right.Thanks for your efforts. I really do appreciate it
So with all that said, I am assuming my slide/frame is correct.
Everything else is.

The fact that everything else on your pistol is correct also helps support your frame and slide being original to each other. Sounds like you've got a winner!

Scott,
What serial number ranges for R-R do you have recorded with color differentiations? I have 179454x with a darker slide and I have seen a few others in the same range with a similar pattern. The small parts all approximate the color of the slide. I'll try to get some pics if you're interested.

I used to have an original finish Remington Rand that had a perfect match of the slide and frame on the left side, but on the right side the frame was noticeably lighter in color than the slide. Yup, the finish on the frame actually was a slightly different color on each side. I assume it was due to long-term storage and the preservative oils used by somebody.

1793xxx and 1807xxx appear to match almost perfectly in slide and frame color as you look at them at first glance. However, if you cock them around at different angles in the light, you can almost see a slightly darker appearance to the slides.
1400xxx and 1496xxx seem to match perfectly. However again, if you cock them around in the right lighting, you can almost always convince yourself of a slight difference...and there may be.
The earliest Rem Rands I've observed that way are some of the 2nd logo Du-Lite guns that have the large NO. Prefix and s/n stamped after finish. These slides do not have the hardened slide stop notch and were clearly produced and finished earlier than some of the frames. The surface prep on the frames on some of these pistols is noticeably rougher, presumably because the prep was generally being done for parkerized guns by that time. But, blued frames were required to go with the blued slides produced earlier. The difference in surface prep and as to when the parts were finished I believe accounts for some slight differences in appearance.
I've also seen a slight difference in the early parkerized pistols, again probably due to the surface prep being done on them at the time guns were still also being Du-Lite blued. There is always an overlap of parts at any transition point in production. These guns seem to extend into late 1943-early 1944.
Also, on the late 1945 guns, a difference can often be seen in the real light gray/green finishes of the slides and frames. From about 2005xxx on, slides will show Blanchard "swirl" grinding marks on them. I believe at least part of the perceived difference in color on some of these guns is due to the different grinding technique, and the way the light hits it when viewing it.
The Blanchard finish grinding appears to get rougher the later you go into 1945. And there seems to be more difference in the colors too. I don't believe Rem Rand was using two different finishes at the same time. I think it all has to do with the surface prep as to how the same finish looks on the various guns.
I need to reiterate that the color differences on original matching Remington Rand pistols is very slight. They all will generally match. Normally, it's only at certain viewing angles that the differences can be seen.
If there's more than a slight difference, it requires a much better look to verify originality. Look at the P proofs and the wear patterns at that point.

RPM How about some pics of the gun with the slight shade variance.