Skirt issue with Prusa Slicer 2.1  

Skirt issue with Prusa Slicer 2.1

Good morning, with my customized CR10S I'm starting to use Palette 2 with object sliced in Prusa Slicer and then given to Mosaic Chroma.

I'm having problems with the skirt...If I have models wich have one only color in the first layer, regardless the number of perimeter I set for the skirt Prusa Slicer always make ONLY one perimeter for the skirt itself and for small object this is not enough to "prime" the nozzle and the first layer of the object start to be printed without significant parts of the outer perimeter...If in the first layer I have two colors so two perimeters of the skirt has been printed, one for color (regardless if I set to print the skirt ONLY with the first extruder) , same thing if i set 3 or 4 perimeters and in the first layer there's 3 or 4 colors. In monocromatic mode the skirt is printed correctly...how can I fix this? 

Thanks!

Andrea