I appreciate the details you shared and your proactiveness in using a JPG or PNG image file format, anke1. I'll provide recommendations to ensure that the logo's background appears pure white in QuickBooks Online (QBO).

The file format could be the reason your logo’s background is displaying as gray. QuickBooks doesn't apply a tint or a template color behind the logo section in Custom Form Styles. Here's what you can do:

• The image file must be smaller than 10 MB24-bits or less
• If your logo is CMYK-formatted, convert it to an RGB image using tools such as Adobe Photoshop before uploading it to QuickBooks Online

For more detailed guidance on adding or customising logos and addressing common issues, you can refer to this helpful article: Add, customise, or remove logos on sales forms.

Kindly reply below or post again if you have any additional questions. I'll keep this thread open to assist you further.