[NTG-context] (body)text colour; presentations (slides): step-wise buildup

Hi, First: Is there a nice way to setup the fontcolour? Currently I encapsulate the whole document with a startcolor/stopcolor block. Second: I want to build up a slide in steps: | first | | first | | first | | | ==[click]=> | second | =[click]=> | second | | | | | | third | If I recall correctly I've seen one implementation for this (in ConTeXt) using JavaScript (and field stacks), but I cannot find anything regarding this. The other possibility (used by all LaTeX packages I'm aware of) is to produce multiple pages: one per step. Does anyone know by heart where the JS method is burried in ConTeXt? Tobias