1) First grind the semolina in a grinder. Now take it into mixing bowl, add curd mix it well and rest it for 20 minutes. 2) Now check consistency and add water if required. Add baking soda and salt. Mix it well. Make a normal dosa consistency batter. Now devide batter in to 3 portion. 1 keep as white, in 1 portion add pinch of orange food colour, in remaining batter add pinch of green food colour. 3) Heat a Non-stick pan, keep the flame low - first add white batter at centre and make circle. After 1 minute apply oil over it. Cook for another 3-4 minutes once it starts leaving pan take it outside.Do same with Orange and Green batter. 4) Tricolor Dosa is ready.