Chart macro's background color turns red when selecting JPG image format

Issue Summary

Selecting "JPG" in image format for Chart macro show the background of the macro in red rather than white.

• Confluence 7.5.1
• Oracle Corporation Java 1.8.0_241-b07

Steps to Reproduce

1. Add Chart macro in a page
2. Edit the properties of the macro and select "JPG" under "image format"
3. Publish the page

Expected Results

The background of the macro should be in white 

Actual Results

The background of the macro shows in red making it difficult to view

Workaround

Change the image format in the properties of the macro from JPG to PNG