Google has updated its logo schema markup guidelines to say it is now required for the logos you submit in the schema looks good on purely white backgrounds.
The new guideline. The new guidelines added a new line to the required properties section that reads “make sure the image looks how you intend it to look on a purely white background (for example, if the logo is mostly white or gray, it may not look how you want it to look when displayed on a white background).”
Where the logo can show. Where does this logo show in the Google Search results? It can show in the knowledge panel, maybe top stories and other areas:
Why we care. If you want your organization’s logo to show up in Google Search where logo markup can be displayed, such in the search results and in the Google knowledge panel, then you want to make sure it looks as intended on white backgrounds.