First, you need to Cross-pollinate Blue Moonflower and Gold Moonflower to get Indigo moonflower. Plant Blue & Gold seeds alternatively in a row. Seeds need to be planted in an alternating pattern in the garden to obtain the new color seeds after they have grown. It will take 24 real-life hours for the plants to grow. Only some of the planted seeds will crossbreed to grow into Indigo Moonflower. To get seeds do not harvest the Indigo Moonflowers at this point. The plants will die after 24 more real-life hours. Once the Indigo Moonflower is dead you can harvest it to get Indigo seeds.