She is showing her true colors.
她终于原形毕露了。
show one's true color 直译过来就是：“露出……真正的颜色”。据说当年英国舰队航于海上时，为避开法国逡巡船队的注意，就升起法国旗帜伪装是自家人，等到关键时刻就改旗易色，显露本色。于是产生了show one's true colors 这个习语，意为“亮出自己的真正旗帜，原形毕露，显露真面目”。因此，当美国人说"She is showing her true colors."时，他/她要表达的意思就是:"She is unmasked."、"She is showing the cloven hoof."。
情景对白：
Benjamin: She is always speaking ill of her partner.
本杰明：她总在背后说搭档的坏话。
Terry: Yeah, she is showing her true color. She is totally a wolf in sheep's clothing.
泰瑞：是的，她终于原形毕露了，她就是一个口蜜腹剑的人。
搭配句积累：
①I was stupid enough to believe her.
我真蠢，竟然相信她。
②I felt the deepest respect for her skill at dissembling.
我真佩服她的掩饰技巧。
③We should draw a lesson here: do not trust appearances; they are often false.
我们应该吸取教训：不要相信外表，外表常常是假象。
④Her seeming friendliness was merely a disguise.
她表面的友好都是伪装的。
单词：
1. show the cloven hoof 原形毕露
Shortly after they became man and wife Tom began to show the cloven hoof.
他们结婚不久汤姆便露出了他的本性。
I thought he would show the cloven hoof sooner or later.
我早就认为他迟早会原形毕露的。
2. dissemble v. 假装，掩饰
She tried to dissemble her anger with a smile on her face.
她试图用她脸上的微笑来掩饰她的愤怒。
I tried to dissemble an interest I didn't feel.
我设法假装感兴趣。
Henry was not slow to dissemble when it served his purposes.
在需要时，亨利会毫不迟疑地伪装自己。
3. disguise n. 伪装，假装
She's adopted so many disguises her own mother wouldn't recognize her.
她如此乔装改扮，连她妈妈都认不出她了。
The supposed prince was really a beggar in disguise.
那个被信以为真的王子，原来是个乔装的乞丐。
Not many people managed to penetrate my disguise.
没有几个人识破我的伪装。
