To make the saffron layer of your Tiranga garden, there is nothing simpler than orange marigolds. Marigolds are widely cultivated in India and can thrive during the rains if planted in well-drained soil. Orange cosmos is another alternative which gives the airy feel to the garden.
Put all the flowers in rows, a raised bed, or a cluster of pots to make a bold statement of color. It doesn’t matter whether you get a botanical equivalent to the flag’s color but it should resemble saffron.