How to set desktop color depth?

inxi says:

System: Host: linux-c55v Kernel: 5.2.3-1-default x86_64 bits: 64 compiler: gcc v: 9.1.1
Desktop: KDE Plasma 5.16.3 tk: Qt 5.13.0 wm: kwin_x11 dm: SDDM
Distro: openSUSE Tumbleweed 20190730
Graphics: Device-1: AMD Baffin [Radeon RX 460/560D / Pro 450/455/460/555/555X/560/560X]
vendor: Sapphire Limited driver: amdgpu v: kernel bus ID: 01:00.0 chip ID: 1002:67ef
Display: x11 server: X.org 1.20.5 driver: amdgpu FAILED: ati unloaded: fbdev,modesetting,vesa
compositor: kwin_x11 resolution: <xdpyinfo missing>
OpenGL: renderer: Radeon RX 560 Series (POLARIS11 DRM 3.32.0 5.2.3-1-default LLVM 8.0.1)
v: 4.5 Mesa 19.1.3 direct render: Yes