Conditional Formatting within a Chart

I basically have 3 sets values that I want to compare in a scatter plot.

Index A: I want the markers for the points determined by B and C to be conditionally formatted (color scale) based on this value.
Index B: This is my X coordinate
Index C: This is my Y coordinate

Help?

Thanks for the response. At that point, how do establish a trend for all data points if they are each in their own series?