I've already made a suggestion quite a while ago about having something to help tell the difference <3 This was back when I was a CC.
My thoughts were something like having a Wifi Signal icon above the torp while it was homing-active. A player would be able to identify quickly if the torps were dumb-fire or not. Also, the icon could disappear when the homing disables as the torps go dumbfire due to proximity to target.
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I do believe the wavy particle effect on homing torps is our solution for helping players identify homing vs non-homing, though I don't believe the particle effect disappears when the torpedo "goes ballistic" for the final bit of distance. I feel that would be useful in helping players understand the homing mechanics and would love if that could be implemented, but no idea on if that'll be a thing.