Custom Inspector Color Spacer

I’m trying to create a colored divider in my custom inspector.

I found this: Unity - Scripting API: DecoratorDrawer


But the resulting texture is always white. I’m using the exact copy pasted code from the documentation.
The color should be Color(1, 0, 0). What’s going wrong?

I was able to achieve the desired result by using:

Color color = new Color(1, 0, 0);
Rect p = position;
EditorGUI.DrawRect(new Rect(p.x-11, p.y, p.width+11, p.height-2), color);