Unseen core/conquered provinces

Let's make a test

Look at the image and tell which provinces of red player are conquered?

Probably it took around 1 second to do so.

Not look at the image and tell which provinces of grey player are conquered?

They are not all core provinces, just part of it, cause it's Germany who invaded Poland.

It's almost impossible to see it. I don't personally see it.

And if You play during day, when there is light around, visibility goes to almost 0, for trying to differentiate core and conquered provinces.

This lines do not work with certain colours