As a side result of the Purple Ranchu Project, I also get the Brown Panda Ranchu. Actually, it is the Purple Ranchu who demelanizes to produce a purple and white fish. The purple gets darker to produce the appearance of brown / light brown. This process is exactly the same as the demelanization process in the blue ranchu to become panda ranchu (Black and White Ranchu).
As this variety is still rare, I think it is better to document it here for future reference. Here are some pictures: