Fix Logo color

Hello,
I would like to know if there is a way to keep the logo (an image) always the same original color (I use the dropdown menu and the free version)

At the beginning the picture shows like that: the colors of the logo have changed. https://zupimages.net/viewer.php?id=20/17/tbul.png

When I scroll down, the logo is displayed correctly as this moment (as I would like to have it all the time.
https://zupimages.net/viewer.php?id=20/17/79t5.png

I do really know if i need to change the opacity or something else…
Please let me know thanks!