Also , as a result of chlorophyll 's relationship to tannin , younger growth is greener and more vibrant in colour , while more developed leaves further down the plant have had their chlorophyll convert gradually into tannin , giving a more bitter flavour and duller brown-green colour profile .

Younger growth is greener and stronger in colour , while more developed leaves further down the plant have had their chlorophyll changed gradually into tannin , which gives a more bitter flavour and duller brown-green colour .
