The first substances has Yin and Yang. All things terrestrial and celestial fall into one of five groups, the Wu Xing (Five Elements). The five elements are...

1 Wood

2 Fire

3 Earth/Soil

4 Metal/Gold

5 Water

The five elements are usually in a state of flux. They can be arranged in a number of sequences, but the two usually encountered are the productive sequence and the destructive sequence.

Productive sequence

1 Wood burns, creating...

2 Fire leaves ashes, creating...

3 Earth contains ore, creating...

4 Metal melts, creating...

5 Water nourishes plant life, creating (back to Wood)...

Destructive sequence

1 Wood draws strength from, destroying...

2 Earth pollutes, destroying...

3 Water puts out, destroying...

4 Fire melts, destroying...

5 Metal chops down, destroying (back to Wood)...

The five elements are also used to symbolize different things:

Wood
Direction: East
Season: Spring
Color: Green

Fire
Direction: South
Season: Summer
Color: Red

Earth
Direction: Center
Season: None
Color: Yellow

Metal
Direction: West
Season: Autumn
Color: White

Water
Direction: North
Season: Winter
Color: Black

I heard that in chinese Blue = Green, how do we distinguish blue from green?

I can understand water being black, because in some places in China the water does look black (Deep and mountains surround). :P

Blue = Green, Green = Blue, this is a great mistake made in the past, and till now, many people still used this equation. :P

Reason, Green is believed to be extracted from Blue, but in actual fact, Green, Red, Blue are the three primary colour of all.

In Chinese, "qing" is actually blue, for examples: "qing tian" - blue sky, "hua qing" - blue colour for Chinese paintings. Green colour should be "lu".

It is not water being black. It should be the element for black colour is water.