As an overview, I was repeating the classic experiment by Shishan C. Chen. The experiment was crossing a blue metallic scale goldfish with a chocolate metallic scale goldfish. My slight modification was that I use the panda metallic scale goldfish instead of blue, noting that panda and blue color has a close relationship. I crossed a panda tosa with a chocolate pompom. I got the panda tosa from crossing panda telescope eyes (which is available in the market) with blue oranda.
The F1 was wild in color. Some turned into wild and orange, and some turned into totally orange color. No blue, no panda, no chocolate appeared at this stage. All have small pompom balls. Interestingly, their size became giants! I took my lesson that crossing far related types of goldfish may trigger the production of large sizes. (This inspires the possibility of doing projects on giant sized goldfish!)
This is the picture of the F1. Picture was taken 5 months ago, and the fishes have grown larger since. The bowl is 40cm in diameter.
Then I did F1 x F1. The results were amazing! I got:
1st category: blue, blue-white combination (or we call it panda) and white (as the blue color totally disappeared)
2nd category: chocolate, chocolate-orange combination, and orange
3rd category: purple (the color in between blue and chocolate), chocolate-white combination (!), and white (as the chocolate color totally disappeared)
4th category: wild color
The shape were all pompom goldfishes. Some with large pompom balls, some with small ones.
I got rid of the wild color early. (And now I regret it, since I would like to know whether it can be used to create red-white pompom combination or not). So, I focused on in-breeding those 3 categories. My utmost desire was to breed and stabilizes the chocolate-white combination, since it is a rarer color compared to the panda. Unfortunately, they do not lay eggs till now even when all the other categories have spawned. My project of creating chocolate-white is in jeopardy! It is not funny to start all over again from the beginning.
The first pair to spawn was the panda. I am happy, since panda pompom is nowhere to be seen nowadays. I was thinking that these panda will produce 100 percent genuine panda color. That is what happen when I crossed panda color with red-white. When I crossed panda with red-white, the F1 was red-white/red. The F2 yield roughly 25 percent of panda. And when I crossed these panda with its panda sibling, the result was 100 percent panda / blue. So, I was hoping the same to happen in this project. Interestingly, the result is different!
Panda color produced from the cross between panda and chocolate, when mated with its panda sibling, does not only yield panda / blue color, but also purple / chocolate-white color in small percentage! I think this is an important matter. It needs someone knowledgeable in genetics to explain this. I do not have that expertise.
These are the chocolate-white goldfish aged roughly three months old. Some have turned totally white. These are the ones that still retain the chocolate color. Aren’t they lovely?
First, I am glad that I do not need to rely on my 3rd category that do not spawn till now. I can still get chocolate-white combination from the panda pair.
Second, let me make clear of the relationship between purple and chocolate-white. For the start, it is better to understand that there are three color involved here: blue, chocolate and purple. Shishan Chen has discussed the difference between them. It involves the black pigmen, the red pigmen, their combination and distribution. Though I do really want to understand more about it and what involves that create the difference between blue and black, chocolate and red, they are not really my stuffs. (I am too stupid for that.) It is enough for me to know that purple is a color between blue and chocolate.
It is also important to understand that there are “base” color in goldfish. I have never read about this. This is my own terminology, that will need help from friends who understand more. This “base” color is what makes the difference betwen black and blue, and between chocolate pompom and purple. Let me explain. In the case of black and blue, we know that differences happen in the melanin pigment. Black ranchu has melanin pigment, so also blue ranchu. But somehow, that same pigment behaves differently in those two. One factor is the different pigment distribution. Is it the only factor involved? I do not think so. But I cannot say anymore about this. There is a second important differentiation between the black and blue, and I want to draw the attention to this. Their “base” color is different. In black ranchu, if the black color fades, we will see an orange color. That is what I mean by base color. Even in Thai black ranchu where the black color does not fade, if we try to scratch the black skin, we will see the orange color underneath the black coat. But in blue color, if the black (or blue) pigment fades, what we will see is white color. So, this is the base color of blue fish. In black ranchu, as the melanin fades, we will have black-gold color (or black-orange), while in blue ranchu, as the melanin fades, we will have black-white color (or panda). So, the base color is different.
The relationship between chocolate pompom and purple pompom has something to do with this “base” color. The base color of chocolate pompom is orange. That’s why, when the chocolate color fades, we will see the orange as the base color. The fish can turn into chocolate-orange,or totally orange fish. We witness the same behavior with black and black-gold fish. In purple goldfish, the base is not orange, but white! So, when the purplish color fades, the fish will have purple-white color combination. And in this kind of combination, the purple color will be more intense, the pigmen distribution will be thicker, and the purple will look like chocolate. That is why I call the purple-white color combination as the chocolate-white. It is the same case with panda, where the blue-white combination is called black-white since the blue is getting thicker and looking like black.
This answers my second point, that is about the relationship between purple and chocolate-white. When the purple color does not fade, the fish will stay purplish. When the purple fades, the fish will become chocolate-white, and some will even turn into totally white.
Third, there seems to be several spectrum of chocolate color in the chocolate-white combination. I am still not sure about this. I am not sure of whether they are worthy to be identified separately.
Fourth, the good news is, when I crossed chocolate pompom with chocolate pompom resulted from this project, the result is not 100 percent chocolate, either! There are purple color also! The same behavior I examined from crossing panda with panda from this project.
Fifth, I have not had chance to cross purple with purple, or purple-white with purple-white. If I do this, will the result yield several panda and chocolate also, or will they be 100 percent purple and purple-white?
Sixth, it will be nice to create purple-white ranchu! A project that is enough to occupy my time for several years ahead!
hermantogoldfish 
Terima kasih pencerahannya pak
I have really enjoyed this discussion about base color
I have the same in ranchu, crystal ranchu, shukin, and veiltails. I believe the purple in this case is not a real purple. It’s a transition. Same for the chocolates in this type. I do not believe this is the same chocolates like in chocolate oranda, at all. Go back to the days of having all blue oranda and ranch u, then some with yellow patches pop up. On time with crosses and fading genes added. The blue fades away and the yellow spots go to orange. I don’t know the answers, but I observe the same. I have even observed my crystal ranch u that appeared blue but had a brown patch nearly its whole body. It transitioned to mostly orange, wherever the brown was.
I believe thenpurple sometimes shows up as the fish is transitioning. It is the least stable color, or shortest lived.
In my previous postings, I differentiate between two kinds of chocolate colors. First kind of chocolate comes from blue, and can coexist with blue. I believe this is what you are referring to. Second kind of chocolate comes from chocolate pompom. This is a different kind of chocolate from the first one, though the appearance is similar. But this second type cannot coexist with blue. When we mate the first kind of chocolate with blue, the result is either blue, blue with patches of chocolate, and chocolate. If the melanin slowly disappear, we will have panda, tricolor, white or redwhite. But when we mate the second chocolate with blue, the result will be wild color, which sometimes turn into orange. There will be no blue, no panda, no tricolor, no chocolate. This alone shows that the genetics of the two kinds of chocolate is different. Only in the F2 there will be blue, panda, chocolate, “purple” and “chocolate white.” In the first category, if we happen to have chocolate, it is not a separate line from the blue, since if we mate that chocolate with the same type of chocolate, we will still get blue or blue with chocolate patches. But if we mate the F2 from the second type of chocolate, there will be absolutely no blue. Hope this clarify the matter. Have a good day.
It is correct that purple behaves the same as blue. It can fade into white. While in that demelanization process, the melanin in blue becomes concentrated and produce the appearance of black on top of white, creating a panda colored goldfish. In purple, the transitory result is brown and white goldfish. Yes, they have the brown patches, the blue might turn into tricolor and end up as red and white. But, it is not always like that. I have seen blue fish, and also purple ones, that do not mutate in a very long time. In fact, I still have them, with age more than 1 year old, and do not seem to mutate. I cannot say if they will not mutate at all, but there is that possibility. Thank you for your comment.