Originally Posted by
DwarvenChef
I don't do alot of asian dishes at the moment so this is speculation...
Cornstarch is the primary thickener in these soups. Geletin will disintegrate at the boiling point, not all at once but rapidly the longer it stays that hot. With the cornstarch you need to bring it up to a boil to activate it, it will thicken noticably at a rolling boil.
The red color alot of times is from the hot chile oils used in these dishes. Food coloring tends to show up at some places as well.