Please look at iAO mql documentation:
double iAO( string symbol, int timeframe, int shift)
Calculates the Bill Williams' Awesome oscillator and returns its value.
Parameters:
symbol - Symbol the data of which should be used to calculate indicator. NULL means the current symbol.
timeframe - Timeframe. It can be any of Timeframe enumeration values. 0 means the current chart timeframe.
shift - Index of the value taken from the indicator buffer (shift relative to the current bar the given amount of periods ago).
Sample:
double val=iAO(NULL, 0, 2);
Note that there are no modes in the indicator so it gives you just one value. No way to tell the color of the line.
To do what you want, get the indicator code here
http://codebase.mql4.com/251 then save it with another name. Compile it and then open the strategy builder and import it.
That indicator has 3 modes, one for the value (it does not draw), a second one for a green color, a third one for a red color. If you see the green line, the red line is zero (and vice-verse)
Unfortunately using this indicator the way you want it is more complex