Hello, I have gone through your query and understand your concern. I suspect it might be due to food poisoning or indigestion. The initial grey colored vomiting is due to mixing of the food you had yesterday and bile. The after some episodes of grey vomitus you had bilious vomiting. Nothing to worry about this. You have to worry if you had recurrent episodes of coffee coloued or fresh blood vomiting. Try to consume enough water and stay hydrated. Once the nausea subsides, take bland diet initially and then normal diet. If the nausea and vomiting continue for 2 or more days, then you must consult a doctor and need proper examination. If you are my patient, i will prescribe some Proton pump inhibitors like Omeprazole with antiemetics. Hope this helps. Please write back for further queries. Wishing you good health.