Actually, yeah, the colors are off. The yellow parts should be green, and the red parts should be very red, and the balls and score should be more blue.
There's old pictures of the display I took years ago here:https://www.handheldmuseum.com/Tsukuda/GamePachinko.htm
But I've had 5 or 6 of these over the years, and they've all been green. I think it's due to an overlay that darkens the screen (the overlay mostly just appears to be 'dark', not really colored, but it definitely affects the color of the VFD.
The first pic is one I just took of the game, the second one is opened up with the overly only covering half of it. Depending on camera exposure, I can see how an uncovered VFD would come out more yellow than green... But the lower half of the second picture is definitely what it should look like.