Thank you so so so very much @Paul_Danyliuk for helping me with this 
!!!
At some point, while testing, I think I managed to get a similar interpolation to yours, but then I couldn’t see how to transpose that to get my desired result 
(maybe I was just too tired… I don’t know…)
I’m sorry this distracted you from your client’s work though 
… But I’m more than grateful that you took that time to help me
As for w3schools…, I agree… It’s not source I would recommend either but yes, they do end up a lot in search results. I just stumbled on that page when I was searching for other svg ideas I could explore within Coda 
. Given my “Coda skills” and the limits I’m trying to push this one seemed like a good exercise to me !
Yes, I know 
. I actually began with HSL(A) (kept the HCL for later…) as I used this post from @Phil_Hamilton as a starting point to explore SVG in Coda
But I took a step back from HSL after a while, when I began exploring color conversions and just decided to get back to “a source”: RGB(A) .
I was testing all this on RGB because that’s where I currently stand in my exploration but it doesn’t mean I’ll keep going into that direction 
.
So, yes, I know it’s a bad idea () but I was still interested by knowing and understanding how to do it, why I couldn’t make it work in the first place and ended up hitting that wall… so I could escape my tunnel vision and improve myself 
!
Thank you so so so very much @Paul_Danyliuk !
I can see things clearly again !!!