Why colors fade due to sunlight or any strong light?

Any material, such as a fabric, paper or even building, emit color due to absorption of incident light and emission of light - the emission wavelength depends upon the electronic properties of the molecules of the material. Over million and millions of absorption and emission, the electronic configuration may undergo changes. This is responsible for color fading of materials due to sunlight or any strong light.

Under sodium street light, why does everything look to have strange unfamiliar color?

The perception of color depends on the nature of light falling on it. Sodium street light is yellow in color. Its spectrum will have only yellow lines and no other color. Hence if yellow light falls on an object, say a person, his skin will look yellowish - different from what his actual skin color is under ordinary white light. Thus under a sodium lamp, such as a sodium street light, everything looks to have strange unfamiliar color.

In fact when a person is color co-ordinating her or his attire, it is essential to know which light will be on the garment, accessories, shoes, make - up color, etc. Because co-ordinating in one type of light, say tube light in a shop, may not have the same spectrum as say a spot light on the stage.

What is shiny black? Isn't it a bit of contradiction?

Black color of an object, say hair, comes about because it absorbs all colors. Many an advertisement of hair care products will talk about ways to get shiny black hair. So how can black color be shiny?

What actually happens is that when you use chemicals to wash or color your hair, they leave a thin coating on your hair. It's like a thin film. The film reflects light, making it look shiny. Hence this phrase shiny– black. The same reason applies to black silk or black horse whose skin shimmers in sunlight.