メリハリ refers to a good contrast between an important/strong/dynamic part and an unimportant/weak/static part.

メリハリがない生活 is a monotonous life. メリハリがついたスピーチをしてください means you should make the important part sound important and avoid a flat tone.

It's a bit difficult for me to explain what's 髪型のメリハリ, but I think it basically refers to some complex/dynamic/lively appearance.

メリハリ is usually written in katakana (or sometimes hiragana). Etymologically, めり (滅り) referred to a low-pitched sound, かり (上り/張り) referred to a high-pitched sound. A kango equivalent of メリハリ is 抑揚, but メリハリ is more often used figuratively.

メリハリ refers to a good contrast between an important/strong/dynamic part and an unimportant/weak/static part.

メリハリがない生活 is a monotonous life. メリハリがついたスピーチをしてください means you should make the important part sound important and avoid a flat tone.

It's a bit difficult for me to explain what's 髪型のメリハリ, but I think it basically refers to some complex/dynamic/lively appearance.

メリハリ is usually written in katakana (or sometimes hiragana). Etymologically, めり (滅り) referred to a low-pitched sound and はり (張り) referred to a high-pitched sound. A kango equivalent of メリハリ is 抑揚, but メリハリ is more often used figuratively.