That multicolor texture is a memory error in your videocard. A texture was not loaded correctly into the videocard or the texture was not read correctly by the videocard or the videocard memory is defective.
This is often caused by the videocard being older or not supported by the game. It can also be caused by the videocard just being old. It can be caused by too aggressive overclocking.
This was a common problem in Fallout3 with nVidia 7xxx series cards, particularly 7800 and 7900/7950 cards, that did not quite properly support DX9.
It would help if you posted what videocard you are using.
It would help even more to replace your videocard if that's possible.