Just asking for colors opinion here from a general perspective, below picture is HM's sweatshirt and I'm considering getting either one of the color, grey or lilac ?

why not both?

I would go for grey.
Lilac is a little too bright for my liking but hey that's just me lah.

Long sleeves doesn’t look good in our tropical climate unless you are a motorcycle rider.

Short sleeves are the way to go unless you ride bikes and want to protect your arms against bruises when you fall.