I did the pallet above on Inkscape, and to the main color (the ones on the current colors column) I add black squares at 20% opacity intervals to darken it to the left, and white squares with the same opacity percentage to the right to lighten it.
As for how I chose the colors, nothing exact, just a first proposal with shades of secondary colors to see if there was merit to the idea. 
I do agree with less variants rather than more though, to give a more concise look.
Indeed, however I am really keen right now in seeing if a convergence towards ubuntu design brand palette is possible.
Little disclaimer here: sorry for not being clear enough this thread is a place to brainstorm this step/goal, find resources, discuss possible problems and how to tackle them, more than provide an actual solution, at least right now. This is really a new thing for me and I thought discussing openly would result in a less error prone activity
Nice
There is no rule which says there should be shades for each colour. You can always use Ubuntu design palette and add individual colours to it. As for Suru icons, maybe maintain a different palette. ie, one for Suru and one for Yaru.
Unless we like to adhere to the Vendor Style initiative 
, as we do
Ubuntu palette itself has 84+ colours. Is that ok for Yaru palette, which will have additional colours + shades ? Is it ok to skip some shades from it ?
No that’s too much
The goal is to match the number of colours the new gnome palette has
Colour system guidelines for Google’s Material design. A good read for us
https://material.io/design/color/the-color-system.html#color-theme-creation
