The Jacaranda flowers can be dry in the shade and ground to get a beautiful blue powder. The flowers bloom in summers.
The blue Hibiscus which is found in Kerala can be dried and powdered just like the red hibiscus
Wet colour:
Crush the berries (fruits) of the Indigo plant and add to water for preferred colour strength. In some Indigo variety the leaves when boiled in water yield a rich blue.