I would call that a "green" that is typical of an "uncolored" youngster. Some types of goldfish take longer than others to "color". Calicos are usually the fastest to get color. Reds take a bit longer. Blues can take up to a year in the varieties I have.
I would guess that you will be seeing a red, metallic fish when that one "decolors" or gets its beginning adult coloration. IT could have some white on the belly - but that may drift or decline as the fish ages.
Since it has a fairly straight back, I would call that one a "Lionhead" for Ranchu are supposed to have a more curved back. It needs to develop a full headed wen to be a true Lionhead - and it is too young at this time to tell what type of wen it will develop.
I would suggest feeding it heavily on protien to help develop a wen.
Other than that, that is a nice healthy little one you have there.