[amibroker] How to change color of bar?

[cstdc5588]

I'm testing the indicator of vwma10. But the up bar have red color and 
down bar have green color. I want to change up bar to green color and 
down bar to red color. How can I do it? Below is the formula of vwma10. 

Graph0 = Sum((Volume*Close),5)/Sum (Volume,5);

Thanks!