Rain is symbolic. There can be negative connotations associated with sadness and tears, but they can also represent happiness in other ways. I always find rain to be a nice touch in TVB drama even though they use the idea a lot, especially in romantic scenes. In Heart of Greed, rain has been used to represent happiness.
In this episode, Raymond wanted to ask Linda for forgiveness but wasn’t sure whether he should or not. He left the decision to the sky, saying that if it continued to rain the next day, he’ll ask Linda. The next day came; the whole day was cloudy, but no rain. He felt disappointed, thinking he couldn’t yet..but when he left his office, it started to rain ^___^ He really does look like a happy little boy^^ so happy that he called Linda out right away..
“..If Seung Joi Sum can really put behind her sadness; continue to live on with courage, no matter where I’ll go, I know I will have tears of joy …and when these tears fall down; it will change into rainbow-coloured rain, to make her smile…”
The rain scene here happened right after Moses proposes to Linda. The symbolic rainbow-coloured rain represented Raymond’s blessing for the two =)