Is vomiting bile I think its called (a greenish yellow liquid common to come out first if dehydration is the problem?

Nah. Normal vomiting of stomach liquids is a bright, overall clear, yellow fluid. Bile is a deep solid green that suggests an obstruction below where the common bile duct enters the bowel. Neither is a symptom of dehdration but can lead to it if ongoing and unable to tolerate fluids. Symptoms of dehydration involve dry mouth, fatigue, thirst, decreased urine, and dark urine.