This colour decision is a mirrored image on the goddess's intense and protecting character, together with her power to bestow blessings and victory upon her devotees. Delighted with Vishnu, the goddess appeared and brought forth her manifestation Bagalamukhi with the lake. Bagalamukhi calmed the storm, restoring purchase within the universe. https://www.youtube.com/watch?v=IOlRdolK0uM&t=74s