Changes to CollisionShape2D debug color project setting are not applied due to the previous default color being considered as custom

[Calinou]

Tested versions

• Reproducible in: 4.3.dev b091162a9

System information

Godot v4.3.dev (4a0160241) - Fedora Linux 39 (KDE Plasma) - X11 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4090 (nvidia; 550.67) - 13th Gen Intel(R) Core(TM) i9-13900K (32 Threads)

Issue description

Changes to CollisionShape2D debug color project setting are not applied due to the previous default color being considered as custom:

https://github.com/godotengine/godot/assets/180032/8208ad7a-e514-4271-9f89-69f448f64b34

To resolve this, I suggest using the RayCast3D custom debug color behavior instead:

An opaque black color is considered as being "no override". In practice, you'll almost never want a debug shape to be opaque black – and if you really want to, you can use #010101 or #000001 anyway.

Steps to reproduce

• Create a CollisionShape2D with a CircleShape2D.
• Change debug shape color in the project settings.
• Select another node and select the CollisionShape2D again to force the inspector to update.
• Notice how the default debug colors becomes considered as a custom debug color in the CollisionShape2D inspector, which means 2 things:
  • The new default color isn't automatically applied; you have to click the reset icon instead.
  • The old debug color is written to the scene file as it's a non-default value.

Minimal reproduction project (MRP)

N/A

[dalexeev]

• See #39072.

I think in practice you rarely change the project setting.

To resolve this, I suggest using the RayCast3D custom debug color behavior instead

This option is inconvenient because you need to manually change the alpha channel. For a ray cast it's not necessarily as it is a line, but the collision shape is a figure. Alternatively, we could use PROPERTY_HINT_COLOR_NO_ALPHA, but this would make the alpha channel unconfigurable.