i want to colour my hair but i am scared for damaging of hairs.

It really depends what sort of product you're wanting to use, and what colour you're planning on going for. I'd recommend if you're going for darker hair, to try actually using henna from Lush rather than actually dying. It doesn't damage the hair like some dying does (which can actually strip the natural colour of your hair), but it gives great colour and makes your hair wonderfully shiney.