@Background Pony #5FF9
 
 
そっかふたりとも自分の見てもわかんないもんね
 
“Right, it’s not something you guys would be able to tell just from looking at your own” (RD doesn’t realize that Rarity was implying she and AJ have seen each others’ pubes)

I don’t really know Japanese, but here is my best guess.
 
ねえ気になったんだけどレインボーダシュは陰毛も虹色なのかしら  
RAR: You know, I was wondering, Rainbow Dash, is your pubic hair also rainbow-colored?
 
なっ 急に何言いだすのさ!  
RD: Wha— That’s a pretty sudden thing to say!
 
虹色に決もってるじゃん  
RD: Of course it’s rainbow-colored!
 
答えるんだ!?  
AJ: She actually answered that?!
 
ごめんなさいね私〝たち〟はそんなカラフルなへアじゃないから気になって  
RAR: Sorry… I feel bad that “we” are not as colorful.
 
[匂わせラリジャック]  
[Rarijack vibes]
 
ちょっと…  
AJ: (I guess it’s an “Oh, shush…”)
 
そっかふたりとも自分の見てもわかんないもんね  
RD: (Not sure about this. Possibly “Uh… Even if I’m looking at them I don’t understand.”)
 
[無垢RD]  
[Pure RD]
 
ついでで聞くけど乳首は何色なのかしら? 青? 黒?  
RAR: By the way, though, what about your nipples? Are they blue or black?
 
ちょっといい加減にしてくれる!?  
RD: (I guess something like “You really have no tact at all, do you?”)
 
濃いみず色!  
RD: They are dark-water colored!

Translation?  
The Japanese characters look more Chinese than Japanese so I guess it’s in hiragana or possibly katakana?