How to reproduce:
1. Open the attached “IN-111878” project
2. Ensure the 2D Tilemap Editor package is installed
3. Open the Tile Palette window (Window > 2D > Tile Palette)
4. Observe the Tile Palette color and grid
5. Navigate to Edit > Project Settings > Graphics
6. In the Default Render Pipeline setting click the 'x' next to “UniversalRP (Universal Render Pipeline)” and double click on “None”
7. Observe the result

Expected result: The Tile Palette background and grid remain the original color
Actual result: The Tile Palette background and grid become lighter

Reproducible with: 2023.1.0a1, 6000.0.55f1, 6000.2.0f1, 6000.3.0a4

Reproduced on: Windows 11
Not reproduced on: No other environment tested

Note: In 6000.0.2f1 and below, the background and grid become darker when using the Built-In Render Pipeline and lighter when using URP