Schematic editor: netclass color of wires and default sheet background color eventually turns black.

Description

After working on a schematic, eventually, all wires turn black.

A new wire was just drawn at the right side:

After pressing F5:

In Schematic settings, the netclass' color changes from transparent black (default) to opaque black:

If color is reset with "Clear Color", wires will look green again.

Maybe related: #9628 (closed), #10579 (closed)

Steps to reproduce

1. Work on a schematic
2. Notice that wires have turned black
3. Open Schematic settings, and see that the netclass color changed from transparent black (default) to opaque black.

KiCad Version

Application: KiCad Schematic Editor (64-bit)

Version: (6.0.6), release build

Libraries:
	wxWidgets 3.1.6
	libcurl/7.82.0-DEV Schannel zlib/1.2.12

Platform: Windows 10 (build 19044), 64-bit edition, 64 bit, Little endian, wxMSW

Build Info:
	Date: Jun 18 2022 23:26:20
	wxWidgets: 3.1.6 (wchar_t,wx containers)
	Boost: 1.79.0
	OCC: 7.6.0
	Curl: 7.82.0-DEV
	ngspice: 37
	Compiler: Visual C++ 1929 without C++ ABI

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON