Got it — that “flash of light background” when switching to or loading dark mode is a common issue, and you’re right that it’s usually a kind of FOUC (Flash of Unstyled Content).
Before diving into fixes, could you share the following?
1. The way you’re currently handling dark mode (e.g., CSS prefers-color-scheme, JS toggle, or CSS class like .dark on <html>).
2. Whether you’re using a framework (like React, Next.js, Astro, etc.) or plain HTML/CSS/JS.
3. The part of your code that sets the dark/light theme (HTML head + relevant CSS/JS).
Once I see that, I can pinpoint why the flash is happening and give you an exact fix (for example, inlining a script in the <head> that applies the theme before paint).
If you want, you can paste or upload the code for:
your <head> section, and
your dark mode script or CSS toggle code.
Would you like me to explain the general reasons and fixes for this issue first (so you can understand the concept), or do you want to go straight into fixing your specific code?