I used to bred my salamander HMPK male x purple bf HM female....i get three kinds of colour, one of them just like this....
is there any comment? why i get this colour??

i would guess its becuase your salamander was breed originally from Bicolors with those colors, and the "purple" butterfly was most likely from a Royal blue marble spawn becuase isn't purple now mostly royal blue fish with some sort of red wash making them appear purple, but I'm new to the betta world just my guess. I'm sure you will get alot more theories. ^_^

I would say that your boy is somewhere between having yellow wash, and having MG characteristics.
Obviously, both parents carried yellow, and that is why this fish has yellow on him. Salamanders are a type of bi color, which is why he came out with the mg type pttern, but you see, it really isn't enough color, making it look more like wash than a BF MG.
The mother was likely to have been a red washed royal.. which is why he came out blue.

It was my understanding that salamander was originally derived from MG bi colored betta so it is simply reverting back to that.

Basicly, same thing they said!
;) :P