itifonhom: ...when I see the see-through crosses on MvR red Albatros, I think that may these paints have been a bit transparent.
The opacity of colour paints varies within the same company products.
It depends on the colour tone itself.
All "glowing / shining" bright colours, like yellow, orange, most reds, yellow-green etc.,
don't contain any "dirt" greyish additions, as they are added to more "broken" colours.
So, the less "broken" a shiny bright colour is, the more will it shine through.
MvR's red could not cover a black cross in one layer; but they had problems getting enough
red to paint whole aircraft, already. So they haven't bothered to coat it thicker.
And still, without an underlying coat of a more opaque colour, it would have shone through.