These are samples of modern acrylic paint matched to the original chipset. I have seen Thomas Chory's book and there are only actually 3 RAL 7028 variants as the first one, Dunkelgelb Nach Muster IS NOT RAL 7028.
The first one came into use on new vehicles in February 1943 and was only used until the end of Operation Citadel, the battle of Kursk. It was never entered into the RAL Register and the colour was changed after feedback from frontline troops, but the name wasn't changed.
Dunkelgelb Nach Muster translates into Dark Yellow after Pattern/sample.
The first actual Colour that was registered as RAL 7028 was the second colour above. It was changed to the brown that is very similar to the Afrika Korps RAL 8000 and to the final shade which was given a field trial by Tiger II tanks with a RAL 6003 Olive green base coat taking part in Operation Panzerfaust in Budapest.
You can clearly see that in the photo above, the running gear is not painted in RAL 7028, but the much darker RAL 6003 and on the hull itself you can see that the lighter colour, which is RAL 7028 is clearly darker than the previous incarnations.
These colours were put to use on new vehicles from Christmas 1944 and officially sanctioned in January 1945.
As an owner of original vehicles I do spend lots of time in archives and also with companies that provide me with support and also equipment etc to keep these vehicles in an operational state. Getting the paint right is just one part of it and being able to work with a company that did make the original paint and will still do it for me (to modern standards) is a real boon.
Using the original colours on my currently operating vehicles I was able, last year to hine a Jagdpanther with it's long barreled 88 in a hedge at a re-enactment weekend and with extra camouflage such as a net, bushes tree branches etc may visitors actually walked past the vehicle not realising it was there untill we started it up and crashed through onto the battle area, coming to a stop and then firing the 88mm with a blank and setting off all the car alarms within a mile!
What you have to consider, when you are painting german armour is that the colours used from the change from dark grey are mimetic and the shade will change with the change in light and also the hue will change depending on the base colour. Also our own eyes and subconcious will change the colour too depending on background and distance to try and increase detail.
This picture is my 1/16 Trumpeter Jagdtiger painted in the colours above.
The same photo with a black and white period filter applied to that.
Urban background
The dunkelgelb looks a little different as the camera firmware is doing what our eyes and subconcious brain does to try and make out detail and definition. There is still the greenish tinge but it looks more of a dark beige and not as the colour suggests, Dark Yellow!
Here is my complete set
At a pinch, Vallejo's Afrika Korps Model Air paints will be fine as a RAL 7028 replacement as they are quite close and once mixed with the Green and chocolate brown and there is evidence to support vehicles beint pained with those base shades and used on the western and eastern front.
AK's real colours are not real! check out my post on that.