THIRD v3 (smallest Joconde of the world)

The smallest Joconde of the world !

v1 :
WEBP = 176 KB / PNG = 256 KB
v2 :
WEBP = 192 KB / PNG = 268 KB
v3 :
WEBP = 173 KB / PNG = 245 KB

I managed to build an image into 2 RGB channels, instead of 3 RGB channels, which results in considerably reducing the size of the files.

Moreover, I used 3 different methods
(I'm not sure that it would be possible to improve v3 only on 2 channels)
Click here to view the comparison between v1 & v2 & v3 :

In the same collection :
FIRST
SECOND v1
SECOND v2
THIRD v1
THIRD v2
THIRD v3