when I want to change the white base color of a material, the color picker jumps always to the middle of the color list, to a second white. Then I have always to scroll up to the base colors.
The white of the default material isn’t a full-white. That is because in real-life there isn’t such a color (nor is there a complete black).
This is a deliberate, not a bug.
edit: for rendering you should always try to avoid using any channel being either 255 or 0 - you should always aim for something below 255 or above 0. It’ll make your renderer software happier.
Then I would like that you just suppress this jump to this light-gray. In the end I would like to start with the top base colors in the list, and not always scroll up. Please take a look at Rhino 5, there the list starts always with the base colors.
You might consider adding the color you want to the Rhino colors.txt file, this help topic discusses how to modify the file. I noticed there is a bug in the documentation, the actual file name is “colors.txt” not “colors_languagecode.txt”