I’ve seen this a lot on the back of Pokemon cards as well, with the blue borders.
My initial thought was during the printing process there were two machines which painted the borders, vertically and horizontally. The result of the look was due to an inaccurate mixture of paint and the inability to exactly match the two yellow and blue colors accurately.
I feel like I’m wrong 
Anyone know the true reason for this?
I have cards that look like this as well, but I have know idea why. Would also like to know what causes this 
Me when I wear a short sleeve shirt but only sunscreen up to my elbows.
I wouldn’t be surprised if the two printer theory was correct, maybe low ink on one printer instead of poorly mixed color though.
I believe that the printing plates themselves were defective. Modern ‘en masse’ printing is done through litography, a process in which the image is broken down into different layers for each colour which are then ‘revealed’ onto printing plates. Usualy for a colour print you will need four plates (one for each basic colour).
Regardless of what colour they will be used for, they will all have variations of the original image in blue at different hues and colour intensities which will in turn determine how strong a particular colour is. These plates are quite sensitive to light, so if any interference happens while they are being revealed you will get weird lines that eventually transfer onto the paper when printing.
The above example looks like a defective magenta printing plate which resulted in less red coloration at the top and bottom of the border, making it look yellower than the rest of the card. Maybe a bit boring, but if you are curious about it and got 7 minutes to spare the below video shows how the process works:
There might be other reasons for that defect by the way, but having worked in offset printing around 1999 I remember printer plate defects being somewhat common. Probably not so much so nowadays.
@kaldoverde, not boring at all. I wonder if this is actually similar or identical to how Pokemon cards are printed
Interesting, I’ve only ever noticed this on the back of cards. And it seems to mostly just be early WotC-era cards. There are a lot of other distinctive attributes of cards from certain eras (i.e., print lines on EX Dragon Frontiers holos/exs) that it would cool to know more about the origins/causes of.
@two , That is 100% how pokemon cards are printed. Older sets in a bit more rudimentary printers, but through the same process shown in the video.
The reason why I know this is that if you look at pokemon uncut sheets, you can actually see the colour alignment marks on the side which are a distinctive feature of offset printing.
Edit: I was actually able to find the English term for the error, and it’s called ghosting. If you check the link below and scroll down to the picture of a National Geographic magazine cover you’ll see the exact same error:
the-print-guide.blogspot.com/2011/02/ghosting.html
This is 100% it, very good insight. The National Geographic example seems to be the exact same scenario as WOTC also used a yellow spot colour for the border (and blue on the back).
Here’s another video of the offset printing process for those interested. This is from Cartamundi, the company WOTC used. Notice the cards are printed parallel to the line effect on this grimer.
Ive come across this alot. Its only ever on the cards at the top of the binder page, so i think it comes from that little bit being exposed to sun.
Nice
Still kind of strange to understand though in terms of… Essentially the two different color yellows is due to a “Chemical Ghosting” which you cannot see until its too late and the ink is already dry.
This also must mean two different yellows were used, one for vertical and one for horizontal ink? If it was all the same yellow ink then it wouldn’t be two different colors like this @pkmnflyingmaster, @kaldoverde
Good info guys
Only a single roller with a single yellow ink is used for the border. The sheet is fed horizontally and I believe the border is the first thing printed with the yellow spot colour (ie. solid yellow, not CMYK dots).
You need to imagine the full sheet of cards in order to understand how this happens. Along the horizontal axis, The top and bottom borders are rolled onto the sheet continuously for all the cards in a sheet row. In the middle of the card though, the roller is alternating between putting ink down for the left and right borders and putting no ink down where the body of the cards are.
This alternation between putting down ink and not putting down ink can leave a slight excess of ink on the roller such that the left/right border in the middle of the card will come out darker than the top/bottom border that has continous ink application.
That’s probably the effect you see here and how it relates to ghosting
@pkmnflyingmaster, So the sheet gets fed through horizontally and ONLY the Top and Bottom of the margins (yellow) are getting ink on them. Then it goes through a second feeding vertically to get the Left and Right margins?
No, the sheet is only fed through one time for the front side.
The first layer is the border which is solid yellow
The issue of ghosting happens when you quickly change from a high level of colour to a low level. In this case, the top and bottom border of each card are printed in one continuous even application of ink but the middle is not.
The very left-hand column of yellow is printed first, presumably with no problem. Going from the first yellow column to the second column, the ink is not applied where the white is showing, to accommodate where the card will go. This could cause a very slight buildup of yellow ink in the roller and causes the next column to be slightly darker ie. ghosting
Then the card is cut from the sheet and the effect is visible on the final card. Obviously most cards don’t have this so maybe the printer settings were off when that sheet was printed or maybe some other abnormal situation that made the ghosting apparent.
@pkmnflyingmaster , is pretty much spot on here.
It is not that different types of yellow are printed, but that different layers of colour are added once per roller, and the paper is fed through each roller to give you a final image. When you print offset, there are a significant amount of variables at play, printing plate exposure to light, paper humidity, roller pressure, registration (colour alignment), and if any of these fails you will see aome sort of printing defect in the end product.
Because sheets are printed in thousands it would be impossible to quality control them all individually, so usually the person operating the machine takes a sample every 100 or 200 prints (while the machine is still running) and if any imperfection is detected they stop the machine and clean or recalibrate it as needed, starting all over again with a perfect end product.
Usually if quality control is good, they will dispose of any gross printing errors, but if it doesn’t affect the resulting end product that much, it is considered negligible and acceptable.
Lastly, I’ll leave an example below, to clarify how the final product comes to life. As you can see, it is not a matter or printing different tones of each colour, but rather printing 4 basic colours which are then juxtaposed to form a color picture:
Each color you see above represents a different printing plate and a different roller. The sheet of paper is fed into the machine and goes through each roller once, until it comes out the other end as a fully coloured picture.
So essentially the ghosting is build up or doubling of excess yellow ink on another pass, its not a separate run through. @pkmnflyingmaster , @kaldoverde , both gentlemen. Absolute Kudos here
