My question is as per title and more importantly, how to convert regular hex/rgb color format to the one that is used in gnome terminal color pallete (eg #26268B8BD2D2)?
GTK use 16-bit color components. so rgb is represented as rrrrggggbbbb.
The example which you took is equivalent to #26268B8BD2D2 -> #268BD2 -> RGB (38,139,210)
Hope this helps you.