Blue and Yellow...

It just came across my mind... I seriously wonder why actually... You know, in Malaysia context. These two things actually have negative connotation. Only in Malaysia that you can see Blue is the denotation of Pornographic videos/films or even pictures. However, the common denotation of Blue is nowhere near it. If alien comes to Malaysia, they will wonder about it if the local says BLUE movies... So, where does this denotation of Blue comes from? and the origin of this connotation is just too puzzling. Well, the connotation of Yellow is easily identified as dirty, as we can see a lot of dirty things to be in yellow colour. Even so, it is only in Malaysia that you can see people say, Yellow minded a.k.a [otak kuning] ... So, we could see the origin and how the denotation of dirty to yellow. Anyway, yellow minded person is a person with nasty and pervertible mind.... Yeah, I was just wondering how Blue comes to be it... as it is easily explained for Yellow... Based on the surface matter.