Yeah, you can use it but why would you want to.
Seriously though, I've used an SOS mode on one of my drop-in torches coupled with an amber lens for rear-daytime alert use. It really does depend on the circuit though as some SOS ( modes ) on some torches are really slow, especially on the dash-dash-dash sequence.

Currently I use a custom Amber drop-in that has two very good flash modes; one is a nice constant slower flash and the other a series of quick strobe-like flashes followed by a one second pause ( and then repeats ) This is a real attention getter for day time use. Has memory and works great.