HELP!!!, Penumbra Black plauge colour problem

[TaCTiCaLxReFLeX]

I brought Penumbra: Black Plauge installed it and it has this problem:

Spoiler below!

all the setting to the game are on high BTW!

My specs:
AMD athlon x4 3.10GHz
6.00GB ram
Asus Nvidea GTX 550 Ti


AND YES MY GRAPHICS CARD DRIVERS ARE UP TO DATE, JUST DID IT NOW!

PUT THE SHADER ON MEDIUM the shader option should be under graphics