safari browser goes blue
Hi, I've just updated to Safari v15.0. The top part of the browser goes dark navy blue almost black on some sites and intermittently goes white again. I don't want it blue or black I want it the same as the previous version but can't find how to change it. How do I stop the colour changing? I have a Macbook Pro running Big Sur. Thanks in advance.
MacBook Pro 15″, macOS 11.5