Got tired of this black mouse pointer on the black background

Our kitchen radio is an older T-R42 RK3188 Android box with fine Wasser firmware, an LCD monitor and gaming speakers. Good enough for Spotify, YouTube etc. Pity that Google Play Music stops with SEGV.

Another pity is the black mouse pointer on the black background. That is easier to fix, but needs root. Wasser firmware is already rooted.
You can have a look at the mouse cursors by adb pull /system/framework/framework-res.apk (ca. 20 MB). Opening it as a zip file and searching for pointer_arrow.png finds res\drawable-hdpi, res\drawable-xhdpi and res\drawable-xxhdpi for various resolutions. This is what they look like:

So I did GIMP Colors / Invert, replaced the cursor files (alpha shadow is still there):

Then uploaded them aside with adb push /sdcard/Downloads/framework-res.apk and used some su-per powers:

# mount | grep system
/dev/block/mtd/by-name/system /system ext4 ro,noatime,nodiratime,user_xattr,barr
ier=1,data=ordered,noauto_da_alloc,discard 0 0
# mount -o rw,remount /dev/block/mtd/by-name/system /system
# cp /sdcard/Download/framework-res.apk /system/framework
# rm /sdcard/Download/framework-res.apk

They worked.