[Other SmartWatches] BackCheck:
Well, let's get this going. First off we'll start with some current info from my Ticwatch E Shadow (black)

build.prop

#
# PRODUCT_OEM_PROPERTIES
#
import /oem/oem.prop ro.boot.hardware.sku
import /oem/oem.prop ro.product.model
import /oem/oem.prop ro.oem.*
import /oem/oem.prop oem.*

# begin build properties
# begin build properties
# autogenerated by buildinfo.sh
ro.build.id=NWD1.171211.002
ro.build.display.id=NWD1.171211.002
ro.build.version.incremental=4497771
ro.build.version.sdk=25
ro.build.version.preview_sdk=0
ro.build.version.codename=REL
ro.build.version.all_codenames=REL
ro.build.version.release=7.1.1
ro.build.version.security_patch=2017-10-05
ro.build.version.base_os=
ro.build.date=Tue Dec 12 02:54:30 UTC 2017
ro.build.date.utc=1513047270
ro.build.type=user
ro.build.user=android-build
ro.build.host=wphr10.hot.corp.google.com
ro.build.tags=release-keys
ro.build.flavor=mooneye-user
ro.product.brand=mobvoi
ro.product.name=mooneye
ro.product.device=mooneye
ro.product.board=mooneye
# ro.product.cpu.abi and ro.product.cpu.abi2 are obsolete,
# use ro.product.cpu.abilist instead.
ro.product.cpu.abi=armeabi-v7a
ro.product.cpu.abi2=armeabi
ro.product.cpu.abilist=armeabi-v7a,armeabi
ro.product.cpu.abilist32=armeabi-v7a,armeabi
ro.product.cpu.abilist64=
ro.product.manufacturer=Mobvoi
ro.product.locale=en-US
ro.wifi.channels=
ro.board.platform=mt2601
# ro.build.product is obsolete; use ro.product.device
ro.build.product=mooneye
# Do not try to parse description, fingerprint, or thumbprint
ro.build.description=mooneye-user 7.1.1 NWD1.171211.002 4497771 release-keys
ro.build.fingerprint=mobvoi/mooneye/mooneye:7.1.1/NWD1.171211.002/4497771:user/release-keys
ro.build.characteristics=nosdcard,watch
# end build properties
#
# from device/mobvoi/mooneye/system.prop
#
#
# system.prop for generic sdk
#

wifi.interface=wlan0

ro.mediatek.wlan.wsc=1
ro.mediatek.wlan.p2p=1

mediatek.wlan.ctia=0

wifi.tethering.interface=ap0

wifi.direct.interface=p2p0

debug.hwui.render_dirty_regions=false

#
# ADDITIONAL_BUILD_PROPERTIES
#
ro.sf.lcd_density=280
ro.opengles.version=131072
ro.ambient.plugged_timeout_min=10
ro.stem_primary.location.x=0
ro.stem_primary.location.y=200
ro.hardware.sensors=cywee
ro.mediatek.chip_ver=S01
ro.mediatek.version.release=MandWear.W15.26.p0
ro.mediatek.platform=MT2601
ro.mediatek.version.sdk=1
dalvik.vm.dex2oat-threads=2
ro.logd.kernel=true
ro.mediatek.bt.codec=0x02001003
ro.mediatek.bt.sleep=0x00100010
ro.config.ringtone=Atria.ogg
ro.config.notification_sound=Tethys.ogg
ril.specific.sm_cause=0
bgw.current3gband=0
ro.btstack=blueangel
ro.sf.hwrotation=0
ro.mediatek.gemini_support=true
persist.radio.fd.counter=15
persist.radio.fd.off.counter=5
persist.radio.fd.r8.counter=15
persist.radio.fd.off.r8.counter=5
persist.mtk.wcn.combo.chipid=-1
persist.mtk.combo.coredump=no
drm.service.enabled=true
fmradio.driver.enable=0
dalvik.vm.mtk-stack-trace-file=/data/anr/mtk_traces.txt
mediatek.wlan.chip=MT6630
mediatek.wlan.module.postfix=_mt6630
ril.radiooff.poweroffMD=0
ro.mediatek.version.branch=MandWear.wear4
dalvik.vm.heapstartsize=5m
dalvik.vm.heapgrowthlimit=48m
dalvik.vm.heapsize=128m
dalvik.vm.heaptargetutilization=0.75
dalvik.vm.heapminfree=512k
dalvik.vm.heapmaxfree=2m
ro.carrier=unknown
ro.config.low_ram=true
ro.config.max_starting_bg=8
ro.bluetooth.hfp.ver=1.6
ro.config.alarm_alert=Oxygen.ogg
persist.sys.dalvik.vm.lib.2=libart.so
dalvik.vm.isa.arm.variant=cortex-a7
dalvik.vm.isa.arm.features=default
net.bt.name=Android
dalvik.vm.stack-trace-file=/data/anr/traces.txt
ro.build.expect.bootloader=mooneye0.5.30.0.0.5
ro.expect.recovery_id=0x24de3adad7693019978f45406b5fd12d6809a039000000000000000000000000

You'll notice some imported lines from /oem/oem.prop for which I currently have

oem.prop

ro.oem.tw.color=black
ro.oem.tw.theme=Indigo
ro.oem.tw.region=global
ro.boot.hardware.sku=lotus
ro.product.model=Ticwatch E

That aside, the first one I found was a way to change the background overlay color from blue to green or vice versa. Mine was blue (Indigo). This was part of the oem.prop file imported so I had to place it at the begining of the file. The overlay theme files are in /vendor so it may be possible to add more.

ro.oem.tw.theme=Indigo or ro.oem.tw.theme=Green

Happy hunting!