if you use a processing keyword (e.g. "color") as a variable name, eg:

int color = 0xFF;
void setup(){
color = 0x80;
}
void draw(){
background(color);
}

Then you get a error message such as "unexpected token: int" which is
somewhat confusing to the novice. Is it possible to parse this so that a
more helpful message (such as even "unexpected token: color") is given?

noted, thanks. there's a bunch of other ones like this under "PDE /
Compiler & Preprocessor" in processing/todo.txt.