you select some fixtures or directly a group, you locate them, then you open the palettes tab and double click on a palette, nothing!
To apply a palette you've to change one parameter after opening the palettes and change it back to preserve the original value.
All the palette have this issue, the color ones even more:
there is always a difference of one unit from the color you've touched and the color applied > in the example I've touched the blue channel;
The palette opens always in "basic" mode that it's not useful, unless accidentally you click a color and you lose your palette;
To make all this working, the widget color in 2d/3d must be closed, then you open the palette + change the tab to "full" + change a parameter + close it + finally open again the 2d/3d color widget to check if the change has been applied correctly.
For the time being all the palette system is just a prof of concept without any practical utility, it should be considered a key feature in v5.