Your pictures are NOT horrible! The thing to be aware of is that cameras try to achieve a color balance. If you have a white background it will darken the photo and shift the color in what it considers a gray direction.
That's why a gray background is recommended. It's neutral and makes the camera less likely to think it needs to change the colors.
Frosted could be something a maker did on purpose, probably in modern times. Marble King made some of their cat's eyes frosty. Or it could be marbles which spent a lot of time in water, such as in an aquarium.