So can anybody explain to me why In some random areas of the game I see pink textures such as this one?

http://i.imgur.com/tE9uZuf.jpg

Some of the texture assets aren't loading. Try verifying the game cache. You could also have a mod conflict.

See above too. If you have the High resolution Texture pack installed, try to lower your resolution to medium.

It could be your computer specs, can't handle well texture mods on high resolutions !!!

The official texture pack has been known to conflict with other mods though, so you might want to disable that.

Purple texture usually means either a texture is missing from the vanilla files (if a replacer texture was missing, the game would default to the vanilla texture instead of doing the purple no-texture thing),

or you've got an esp that's changing the texture path for a vanilla asset, or you're dealing with a non-vanilla asset.

Try starting a new game without the texture mod(s) present if you have some installed. If you're still seeing purple rocks in the fresh game, then it's a problem with the game or game data itself, not a mod.

If you're not seeing it in the fresh game, that means that a mod has borked the texture path in a way that has effected your saves. !!!