Breeding for colour can be very confusing here I would like to show how it works
Here are the keys you need to figure out the genetics for colour.
BBDD is black
BBDd is black
BbDD is black
BbDd is black carrying recessive
BBdd is grey
Bbdd is grey carrying recessive
bbdd is tawny
bbDd is mahogany carrying recessive
bbDD is mahogany
you can figure out what your mastino is from the chart or go to www.vetgen.com for DNA colour testing.