Translation:The Red River is a big river in Vietnam.
Isn't "màu hồng" the word for pink? Shouldn't it be translated as "The Pink River"?
Hồng is the word for pink, but The Red River is the English proper noun for this river. I'm not sure for the reason for this, but I would love to know.
I'm going to guess it's because "red river" sounds better in English due to alliteration, while "sông hồng" sounds better in Vietnamese due to rhyming. The actual color is probably somewhere in between.
Hồng is a Sino-Vietnamese word from 紅 which means red. the English name comes from its Chinese name 紅河, as it's a river that flows from Yunnan in Southwest China through Northern Vietnam to the Gulf of Tonkin.