Different colors in the background

### Describe the bug
While watching the new video of [**But what is the Central Limit Theorem?**](https://youtu.be/zeJD6dqJ5lo). At *11:45*, one may notice a darker box at the left side of the screen:

In the left part of the screen is `#010101` while the right is `#090b08`.
Wondering if this is a bug in rendering.
### Additional context
This error is noticeable only on *some* devices, not all devices can see this error (like on my phone).

The issue points to a rendering inconsistency in a video at a specific timestamp. Start by examining the video rendering pipeline in manim, focusing on background color handling and scene composition. Look for code that sets background colors or applies gradients. Reproduce the issue by rendering the referenced video segment and inspecting the output frame colors. Check if the discrepancy is due to device-specific rendering or a bug in the color application logic.

索引モデルが issue の本文から書いたものです。