I can understand that for people from the “technical department” current color selection may be good enough for selecting colors for layers but you are working on rendering capabilities of Rhino so you may be more interested in enhancing it.
The same Select Color window is utilized in the material creation as in layers so it crosses territories
There are many approaches for color selection across different software and many places to take inspiration from.
Since I’m a bit into digital painting I am using Coolorus plugin for Photoshop.
Probably all of those functionalities inside Rhino would be overkill but some of them are really cool concepts to get familiar with.