From Fedora Project Wiki
The Fedora Remix Design: Usage Guidelines
In order to protect and grow the Fedora brand, we have a distinguishable Fedora Remix design that can be used without permission to mark content that is derived in part from Fedora. There are guidelines for the design's appearance and usage, outlined here.
Design Usage
Improper Design Usage
Never Switch the Colors
Never Use the Design on Similarly-Colored Backgrounds
Never use the design on similarly-colored backgrounds. Use a choice from the palette that is appropriate for the background.