The transition on the username color change when the background changes is noticeably slower than the "Donate" and the "Get AI Guide" transitions.
1. Go to any subject page.
a. Note that the top header bar is dark blue and the letters are white.
2. Hover your cursor over the header bar.
a. Note that the top header is white and the letters are dark blue.
b. Note that the transition of the username from white to dark blue takes noticeably longer than the color transitions of the other tabs.
I have noticed this issue in multiple browsers and operating systems.
Because the issue is a transition, I was not able to get a screenshot of the issue. Here is the location of the issue: