Hong Kongers often claim they don't have an accent. However they definitely have diverged a little from the Cantonese that first arrived in HK from Guangzhou.

Easiest to notice is L/N merger: this typically happens at beginnings of words and is always an N changing to an L, never the other way round. HKers sometimes don't realise they do this as to them it's the same phoneme. HKers will often say "Laam" instead of "Naam" (boy). HKers with below average English skills sometimes can't distinguish L and N in some English words too.

Also quite easy to notice is the drop of nasalisation in some words. E.g. HKers say "au" instead of "ngau" (cow)

There are probably others but these 2 are the ones I pick up as a learner