why do we call japanese yellow skin while some of them have even lighter skin to compare with europeans?

Answer 1

there are different colours in skin that make up the distinctive colour of a persons skin. There is a red colour, a yellowish colour, and a brownish colour if i remember rightly. We all have all of them in different amounts. Asians in general tend to have more of the yellowish colour.

They may have very little of the other colours and thus still be very light skinned.

A european is more likely to have a little of the red colour giving us a pink tinge.

Probably the inaccuracy is calling us white. We should be called pink.

Answer 2

Black people aren't truely "black", but a variety of brown.

But they have some of the darkest skin variations, so they get labeled as the darkest "color".

This is the same thinking applied to asians/orientals and the color "yellow", as well as those of european descent (so-called "whites").

Segregation is a natural tendency in human society, either by sex, color, or creed, or financial status, lifestyle, or kin. It just so happens that skin color is the easiest to identify quickly, and thus gets simple labels like "black", "white", "red", "yellow", "brown", etc.

Because of more recent interratial increases, we are also seeing descriptive labels like "mocha", "olive", and others indicating finer color variations.

I hope this answers your question.