Is it safe to kiss someone who has teeth discolouration that looks permanent? looks like brownish spots all around his/her teeth. or it's contagious? can a person with such teeth get help by whitening such teeth or there's no help at all?

Stained Teeth: Stained teeth can be caused by different factors, including coffee, tobacco, tea, wine, decay, medications, or genetics. None of these items are transferable from one person to another. This person can obviously get evaluated by a local dentist to determine the cause of the discoloration and what is needed to be done to create a more attractive and healthy smile.

Spots: May be from decay (infection), foods (pigments), pre-natal or early systemic disease or specific antibiotics, chemical excess in water/foods, poor oral hygiene, etc. You would be doing the "someone" a favor if you got him/her to seek professional care. Only when his/her oral health is determined can contagion be evaluated.