"Looks like colors have got a significant change...
So, try:
Color registerColor: (Color r: 0.0 g:1.0 b:0.0) named: #white.
and things will be very green."
it would not be making much difference because I am not using color names but RGB values. Also I tried your approach, and though I can change white to another color and see the effect on window the color of the window remains unchangeable and I tried all types of Greys. By the way the veryVeryDarkGrey message had me laughing a lot. I propose the additions of the veryVeryVeryVeryVeryDarkGray and superDuperUberMaxGrey to be on the safe side :D
"Hi.
The default settings are remembered in a class instance variable so that they can be changed according to (user) preference.
If you make a change to #newDefaultSettings you should send #resetDefaultSettings to your theme class
so that they get reinitialized when next required (when an instance of your theme is next created).
Hope that helps.
Regards, Gary"
Two problem with your proposition
a) None of the theme classes use this message in the initialisation
b) MNU
maybe a Pharo 2 message that went MIA ?
In any case I continue to study Morphic and see what will come out of this, not so pleasant , experience. Thank you all for your help.