Cha Bing/Marshall

What a fascinating topic. Very vast. I'll add my bits below for (1)
and (3):

1. Oolong tea is made from slightly more matured leaves with a
different chemical profile, that when processed, resulted in a richer
fragrance. Hence the leaves are larger than green tea.

Black tea and (I think) pu-er teas are made from the Assam variety,
which is faster growing and have larger leaves than the sinesis
variety for the Chinese and Japanese green tea.

Contrary to what you said, shape is a big factor when classifying
green tea leaves. Other ways of classifications are processing methods
and regions of production.

3. Colour depends on many factors, such as origin and processing.
White tea is white because it is covered with hairs, which tea makers
left alone when they make them. Some green tea can appears white. Of
course, black tea is black because of fermentation. Gyugaro is darker
green because they are shaded away from the sun.

Longjing can have different colour because they are basically
different type of longjing, as well as due to age as Marshall kindly
mention.

For Xihu Longjing tea, the yellowish type is ShiFeng Longjing and is
the most esteemed in China. The greenish type is known as MeiWu
Longjing or just Xihu Longjing. They look better but taste less good.

They are lots of fake Shifeng Longjing - people would over pan fry
them yellow to sell them as one.

Hope it adds to the discussion.

Julian
http://www.amazing-green-tea.com