Can you tell the difference between Japanese and Koreans?
Can you differentiate between Japanese and Korean people?
この場合、次のような言い方ができます。
ーCan you tell the difference between Japanese and Koreans?
「日本人と韓国人の違いがわかりますか?」
ーCan you differentiate between Japanese and Korean people?
「日本人と韓国人を見分けられますか?」
例:
Can you tell the difference between Japanese and Koreans? If you can, what is the difference?
「日本人と韓国人の違いがわかりますか?わかるなら、違いはなんですか?」
ご参考まで!