Change background color for a section of a graph

Hello,
Can you please, provide more information regarding graph you would like to modify?
What type this graph is? Column, bar, bubble etc.
If it possible, can you please, provide screenshot of the graph ad mark area you would like to color differently.
Thanks

I am using bubble graph. Take a look at the attached image top right corner. It shows a different color. The image backround color is painted for demonstration purpose.

Hello,
I have started investigation and come up with 2 more questions:
1. Are x and y scales always show same values? Or user can change them while report is displayed?
2. How target is calculated?

1. x and y scales always show same values
2. The target is fixed hard coded value

Here is the way it is not ideal, but enough for fixed target value.
1. In the chart select x and y axis, and in its property winfow set maximum and Minimum value for both
2. Draw an image that can fit the chart's scale and target
3. Put this image to the folder: <insight_install_dir>\AppServer\profiles\RationalReport\installedApps\<node_name>\IBM Cognos 8.ear\p2pd.war\common\images
4. Set the image as the background image of the chart body.
a) Do not forget to unlock first!
b) While setting background image, do not browse for it, type full path directly: http://hostname:9080/insight/common/images/backgound_image_name.png

If the image is not shown when running the report, wait for a few hours or re-start WAS service