"And what is that?" - "This is a blue light!"

...no more and no less!
UV light (about 395 nm) with a very strong proportion of blue light!
Pretty nice as a gimmick and the rapid test of greenbacks!
For those who would like something "more professional", I can only point to lower wavelengths, to housing: a "Euro-8 lamp referring to" - the article is indeed "instead of: 17,50 EUR Now: 8,66 EUR" - this lamp, however, should really have ever tasted EUR 17.50, I hope that she has no one bought at the price, because the price is, in my opinion, not worth much !!
The EUR 8.66 are quite acceptable; Although the housing sits stably on screwing one notices immediately, however, that the product is (again in my opinion) settled qualitatively rather in the lower sector. From time to time the lamp is off times, then you have to unscrew it and screw back easy apparently the contacts do not always ...
Otherwise, it does exactly what is their job, it is lit, with a regular light, no defective LEDs.

EDIT 8 months later: batteries discharge when not in use in about one to two months. -> Better take out!