It is the 1930s and 1940s and the qualities of the printing inks back then were not as efficient as they are now. Some colors (like white) were not opaque enough and to reinforce them there were two possibilities: either we passed a 2nd layer of white or we added behind a silver or gold layer.
look at these original unused decals:
here a tricolor decal from 'Franz Heinrich Schmidt' printed right side up. Observe the white, there are 2 superimposed layers.
And on this back printed decal from 'Hubert Jordan', there is only one layer of white reinforced by the silver layer (more dull than the silver of the WH decals). This silver layer will be applied on the helmet side.
This decal is constructed as follows: against the paper a first layer of varnish which is a little larger than the decal. This is what we call in the printing world "or overprint varnish" or 'transport varnish', compulsory in the manufacture of a decal. then there is a layer of black and red. On top comes the layer of white. White is used as white in the color of the tricolor but also as a background color and reinforcement for the red tint. Then finally the silver layer to reinforce the white.
Please note that on luftwaffe decals from 'Hubert Jordan' printed backwards you can find silver or gold layers.
On your 1st lacquer decal order
you will receive small decals to practice using the glue