The observed problem with engine paint colors is that they often do NOT exactly match the OEM colors. OEM colors which, by the time we are seeking to match them, have faded a bit from heat cycles and possible oil contact.
When I was spiffing-up my '67 Newport 383 4bbl engine, it was in the earlier 1980s when the only Chrysler engine paints available (from Mopar Perf) was "HEMI Orange" and "Chrysler Blue". So, I went to the local auto supply that also did automotive paint. I told the owner what I was wanting to do, so he dug out his old paint chip chart book. We were looking for a factory color that could be the basis of tinting it to match the Chrysler "Turquoise" color. Surprisingly . . . it turned out to be a '67 Dodge Pickup truck color named "Desert Turquoise" AND it was an exact match. So he built me a quart of it in factory acrylic enamel. A great surprise! It was a great match, other than the very slight fading of the OEM engine paint (which was usually a normal base enamel rather than the exterior-use acrylic enamel.
In the world of automotive engine paint, several different colors of the same color name can and do exist. What Krylon might sell for Chevy Blue (for example) did not match what VHT might sell for Chevy Blue, NOR did either one really match the OEM Chevy Blue (which GM Parts sold at that time). The Krylon item was much darker, closer to a real "Ford Blue", by a big amount, by observatrion. We all knew these things back then, but few mechanics just wanted some paint with the correct name even if it was not the correct color for the color name. Even when the restoration industry got a lot larger in the 1990s, even the (claimed to be correct) spray paint sold by a vendor with "Restoration" in their name were not the exact matches we were desiring.
Reason for these mis-matches and such? The OEM engine colors are a part of the basic "copyright" for the entire vehicle. So, unless the colors were sold by the OEM themselves, they would not be an exact match UNLESS they were LICENSED by the OEM for resale by the vendor (with appropriate notations on the item itself).
So, unless the particular paint color is licensed to be correct, it can be just a bit off in color. Some more than others, by observation. Which can also vary as to the "lot" of when the color was formulated. But some of the OEM-sourced colors seem to be a bit off to me, too, which might be due to the fact that we don't worry about color accuracy until years later.
End result, if you desire an exact match in engine paint, take a clean valve cover down to a local paint supply house and get a pint or quart of it mixed to match what you have. THEN you can thin it appropriately and put it in a Preval spray bottle and spray it on. Or use a quality small oil paint brush to apply it that way.
About twenty years or so ago, there was a big hoopla when a judge counted off for "incorrect engine color" at a national car event. The owner complained, but there also happened to be a few original cars at the meet, which became the "standard of comparison" for the color. The paint vendor was also there, too. As it turned out, the paint vendor had used an incorrect sample to base his inventory on, so what he claimed was correct was not . . . but that was fixed soon thereafter.
Seems like there are a few threads in here on what other members have found to work well for them and their particular engines? Plus some charts online, too. PLUS, of course, Mopar Performance's Restoration Parts catalog (IF they are still doing that).
Some thoughts, experiences, and observations,
CBODY67