Add salt and ajwain in wheat flour, and mix it.
Separate the flour in three portions.
Add spinach purée in one portion, and carrot purée and haldi in another portion.
Add very little water in the third portion. (Puri dough needs to be stiffer than the chapati dough. So add less water than you would while kneading chapati dough. Don't add water in the green and orange dough; the moisture in the purées should suffice.)
Heat 5-6 tbsp oil, when it heats up add hing and turn off heat.
Add 1/3rd oil in each portion of the flour and knead stiff dough.
Make two balls of each colored dough.
Roll out a roti of approx. 6 inches in diameter using 3 different colored balls of dough.
Now lay down the green roti on the chakla (wooden board) and spread a bit of oil all over it.
Dust the green roti with a bit of flour and then lay the plain wheat roti on top of it.
Spread a bit of oil over the second roti and dust it with flour.
Lay the orange-colored roti on top of the second roti.
Roll out all three rotis together to form a slightly bigger roti. (Approx. 10 inches in diameter.)
Now roll the 3-layered roti tightly. (If you make a loose roll, there will be gaps between the different layers in the puri.)
Cut the roll in 1-inch pieces.
Lay each piece on chakla with the different layers visible from the top, and roll it with the rolling pin to form a puri.
Repeat steps 8-16 to roll out puris using all the dough.
Poke the rolled out puris using a fork. (This will prevent the puris from puffing up while frying. If the puris puff up the different colors will blend and not be distinct.)
Heat a kadai and when the oil is sufficiently hot, add one puri in it. (To check whether the oil is hot or not, I put a wooden spoon in the oil. If bubbles form near the spoon, it means that it is properly hot.)
Fry the puri till it gets properly cooked, use the zara (slotted ladle spoon) to gently splash some oil on top of the puri to ensure the top side cooks properly too. (I didn't flip the puri while frying as the side at the bottom tends to brown a bit, and I wanted to retain the colors.)
Fry all the puris one after the other and lay them on a tissue paper to blot out excess oil.
Serve them hot or cold, with curd or pickle. Grownups can even have them with tea.