“近朱者赤，近墨者黑”，汉语成语，字面意思“What’s near cinnabar goes red, and what’s next to ink turns black”。比喻接近好人可以使人变好，接近坏人可以使人变坏。指人容易受客观环境影响(be influenced by one’s surroundings)。
与英文谚语“if you lie down with dogs, you will get up with fleas”意思相近，表示“If you associate with bad people, you will acquire their faults”。
I worry about my brother hanging out with all those troublemakers—if you lie down with dogs, you will get up with fleas, you know?
A: It’s not fair. I’m starting to get a bad reputation just because I’m friends with Suzy and she has a bad reputation.
B: It’s only natural. People think that if you lie down with dogs, you will get up with fleas.