Main music theme of this part is "Run" by Ludovico Einaudi (start listenting to from 2:53)

Symbol meanings I'd like to point out:

❄ Winter symbolizes lineliness and despair. It is also a period of self-reflection and preparation for a new beginning ahead. Snow is associated with changing and transformation.

💛 Marinette's dress colour is yellow in this part. No, she doen't copy Chloe. Despite the fact that yellow is usually associated with joy and warmth (at the moment the girl is far from being happy), it also is a colour of cowardice and extra sensation.

🌼 The flower given by Luka isn't a rose. It's a chrysanthemum (or shortly, mum). In the language of flowers mums express sincere sentiments and carry a symbol of devoted love and loyalty. It's Luka's way to say that he loves Marinette. At the same time mums are frequently gifted to friends which underlines that Luka isn't in the situation to declare his affection freely, so they still keep on being friends.
Speaking of the colours, I decided to combine several in one:

🧡 Orange - happy feelings and good vibes - a reminder of their happy childhood and joy they shared growing up together.

💗 Pink as a symbol of affectiin is used to tell a friend that they're extra special for you.

💛 Yellow means sorrow and neglected love. Marinette doesn't accept the flower. In the end you can see Luka keeping it while she is going away with Adrien.