Going by the story of Samudra Manthan, we find that Samudra Manthan produces both Amrita (elixir of life) and Vish (poison). Seekers, travelers of spiritual path directed Amrita towards kundalini awakening and full awakening of results in one becoming an enlightened one.
The Vish (poison) just could not be discarded and has to be retained in the body causing the whole body going blue. It can also be retained in the neck resulting in neck collar going blue or even developing throat cancer as happened in case of Sri Ramakrishna Paramhansa.
Samudra Manthan allegorically is a battle that ensues within every human being every second of life. The battle is between positive and negative forces of nature. Seekers were more positive than negative, hence more Amrita was produced and it became easier for them to awaken kundalini shakti early.
Those with a totally negative attitude lost their race in life, blaming God all the time. Lord Krishna is the soul atman existing in our heart. Remaining truthful we can take guidance of Lord Krishna at every stage of life. Indulging in spirituality gradually we can overpower negative forces, win the battle of Mahabharata eventually.
For a spiritual traveler there is no cause for harboring negativity of any kind. We are Arjuna. The battle of Mahabharata, Samudra Manthan goes on within us. To overpower negative forces of nature, we have to establish control over five senses and mind. Only then our kundalini awakened fully. We also need demolishing our ego in totality.
To win the battle of life, to become an enlightened one we have to win the battle of Dharma within. There is absolutely no escape from this cycle of life.
Any seeker in search of God finally succumbs to death with cancer of throat or the whole body going blue. Either we retain Vish (poison) in the neck or let it spread all over the body making it blue.
Praying to Krishna, worshipping Krishna does not mean anything. It all the time resides within us as our soul atman, the spirit, consciousness within.
Bhagavad Gita was all about how human beings should balance their life both external and the inner journey.