Thanks for the tip, I didn’t know that.
Unfortunately the adb shell cmd overlay enable com.android.theme.color.purple still gives an error.
I found the command: shell cmd overlay list which results to:
com.android.networkstack
[x] com.android.networkstack.overlay
android
[ ] com.android.internal.display.cutout.emulation.corner
[x] org.lineageos.overlay.customization.blacktheme
[ ] com.android.internal.display.cutout.emulation.double
[ ] com.android.theme.icon.pebble
[ ] com.android.theme.icon.square
[ ] com.android.internal.systemui.navbar.gestural_wide_back
[ ] com.android.theme.icon.vessel
[ ] com.android.theme.icon.taperedrect
[ ] com.android.internal.display.cutout.emulation.hole
[ ] com.android.internal.display.cutout.emulation.tall
[ ] com.android.internal.systemui.navbar.threebutton
[ ] com.android.internal.systemui.navbar.twobutton
[ ] com.android.internal.systemui.navbar.gestural_extra_wide_back
[ ] org.lineageos.overlay.font.rubik
[ ] com.android.theme.icon.teardrop
[ ] com.android.theme.font.notoserifsource
[ ] com.android.internal.display.cutout.emulation.waterfall
[ ] org.lineageos.overlay.customization.navbar.nohint
[ ] org.lineageos.overlay.font.lato
[ ] com.android.theme.icon.squircle
[x] com.android.internal.systemui.navbar.gestural
[ ] com.android.theme.icon.roundedrect
[ ] com.android.internal.systemui.navbar.gestural_narrow_back
[ ] com.android.internal.systemui.onehanded.gestural
com.android.launcher3
[x] com.android.launcher3.overlay
com.android.wifi.resources
[x] com.android.wifi.resources.fairphone.FP3
com.qualcomm.qti.poweroffalarm
[x] foundation.e.poweroffalarmoverlay
com.qualcomm.embms
[x] foundation.e.embmsoverlay
As the commands related to accent colors are not listed I think it means that its not available.