the stomach contents can be definitely be bright yellow when empty of most food. this is the normal stomach/gastric fluids. as far as those brown tube-like things i really can't comment since i did not see it. if your vomiting subsides i would not be overly-concerned but if your are continuing to vomit please consult your medical provider for advice. someone who knows you and your medical history.
i just vomited and it was just yellow liquid and i did it three times. i know this sounds weird but also 6 brown tube like things that i threw up. since it was my vomit and i was scared i touched one and it was a jello consitency