Mak kau hijau
"Mak kau hijau" is a Malay phrase which literally translates in English "Your mother is green".

This phrase origin came from a video that went viral in Malaysia about 2 kids was insulting each other. One of the kid spontaneously said "Mak kau hijau" maybe because out of words after being insulted and angry at same time. The reason it went viral because that phrase has no meaning of insult at all and it is funny when he said that. That is why netizens of Malaysian keep spamming each other with this phrase at that time more just like to joke with each other.

The phrase itself has no insult meaning but when foreigners comment something bad about Malaysia, they will get floods of reply "Mak kau hijau".
Hey bodoh, mak kau hijau!
Hey stupid, your mom is green!