Blue light in a fridge. Is it really beneficial or just marketing?
Maybe a little bit?

There are two claims here, so let's talk about them individually. I'm not sure how this light is being produced (probably LED), but it'll have a wavelength somewhere between 400 and 500 nanometers.

Reduced bacterial presence:

The intrinsic antimicrobial activity of blue light is well documented. Although the mechanism is not entirely understood and widely debated, the commonly accepted hypothesis is that the blue light triggers the production of reactive oxygen species like singlet oxygen that are highly toxic. However, this has only been observed under high-power light sources, and low levels of light may actually increase bacterial activity. What counts as a high-power source, you ask? The number from this article is $\frac{10mW}{cm^2}$. For a fridge with an internal surface area of >1 meter, such a power source should draw at least 100 W. Given that normal refrigerators use draw 100-200 watts, you'd essentially be doubling your electrical bill for the fridge.

It should also be noted that the above is a best-case scenario. As soon as you add anything to the fridge, you'll reduce the intensity and thus the effectiveness of the light source. Also, the light is unlikely to be on all the time- it probably turns on when you open the door and turns off when you close it. While this helps a lot with power use, it minimizes the effect of the blue light, which is constantly on in experiments.

Larger quantities of vitamins

There's no (reliable) evidence of light of any kind actually creating vitamins, so what the sticker suggests is that it doesn't degrade the vitamins already present as quickly as other kinds of light. 

There's a good article here that discusses the stability of various vitamins. It's worth noting that most of these vitamins and essential amino acids are much more likely to be destroyed by cooking than light, which is probably why the fridge focuses its claim on fruits, which are less likely to be cooked. 

There's very little research that I was able to find about the effect of different wavelengths of light on the stability of various vitamins, but as a whole I remain fairly skeptical that there's any notable difference. Most experiments that do study degradation of vitamins under light subject pure vitamins to high-intensity light for several days- unlikely to happen in your fridge.

TL;DR:

A claim like this shouldn't be a major factor in your buying decision. The effects of the blue light are probably negligible given the conditions in your fridge, but if you've got two very similar choices this feature could act as a nice tiebreaker. Besides, there's a lot to be said about how cool blue light looks and the confirmation bias present in your purchase.