you don;t say what kind of chart you are using, but yes there are ways of doing this. If you are using a bar or column chart then you can assign a fill function that determines an appropriate colour for the bar based on the data value - see the Adobe doc
for some examples. This can be done in MXML or ActionScript.
If you are using a line graph then you will need to do something similar but with Stroke colours: I have never tried this out and it looks slightly more fiddly but should be achievable.
Thank you Richard for the link. According to my requirement i need to go for a line chart & its basically frequency scanner i have develop.So if the area falling in low frequency to be dispalyed as green medim level yellow & above that it must be red.Can i get some more inputs on it.
looking at the docs, there doesn't seem to be an easy way to do different line-segment colours with a line series. So... how about using an area series which _does_ have a fill function property? You do not need to colour in the whole area below the line as there is a minField property that gives you the lower limit of the area just like yField gives you the upper limit. So just as a quick suggestion, set up your data provider with two fields instead of one for y-values, the first being the one you want, and the second one say 10 units (or whatever is sensible) less than the first. Turn the stroke off by setting it to zero width, and use the fillFunction property to colour the area red/yellow/green depending on the value of y.