Photo: 鴛鴦 Milk tea mixed with coffee (by SeetYing)
鴛鴦 (yeen yerng) is a type of drink that is half coffee, half milk tea. The phrase “鴛鴦” is used to describe a pair that is somewhat mismatched.
In Chinese, 鴛鴦 is also mandarin ducks - a reference to how different the male and female look. (On that note, 鴛鴦 can also be used to refer to a couple as ‘lovebirds’.)
If you really must be clear, you can order a 鴛鴦茶 (yeen yerng cha), a mixed “tea”, but servers will know what you mean without the extra word in there.
jyutping: 鴛鴦 = jyun1 joeng1; 茶 = caa4