There are two kinds of turmeric available around the country. Madras turmeric and Alleppey turmeric.
Madras variety is a pale yellow turmeric, best used when you want a very bright yellow colour rather than a strong flavour, for example, when making pickles. It has a very gentle flavour that is good to use with delicate flavoured food like seafood.
Alleppey turmeric is best to use in curries because of its rich and more earthy taste and stronger flavour. Its name comes from the port of Alleppey in South India where the turmeric was originally traded.
Alleppey turmeric is a darker yellow and found in most South Indian dishes.