samples: core: make fallback shader output more distinctive color

docs/changelog.rst

@@ -19,6 +19,7 @@ Changelog
 * Fixed duplicated entries in the Resource Chooser.
 * Changing the sprite in the Sprite Renderer component is now reflected to the Runtime.
 * Added noop resources in ``core/components/noop.*``.
+* Changed the fallback shader to output Color4(255, 0, 255, 255).
 
 **Lua API**
 

samples/core/shaders/default.shader

@@ -571,7 +571,7 @@ bgfx_shaders = {
 		fs_code = """
 			void main()
 			{
-				gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);
+				gl_FragColor = vec4(1.0, 0.0, 1.0, 1.0);
 			}
 		"""
 	}