My friend is looking for a manhwa/ hua, please help! The female lead has brown hair and it...

My friend is looking for a manhwa/ hua, please help! The female lead has brown hair and it can turn purplish and she has powers that when she sleeps she goes to another dimension or place and finds herself in this red hair man’s chambers and at first he’s suspicious but he starts to get closer to her and she sees his portrait in the real world where he has brown hair and what acrually the emperor? Please help!