Whatever makes you more noticeable on a bike, is a good thing. Personally, a dark colored helmet and a dark colored fin are too half a$$ed, IMHO.
Own it. If you want to go with a fin, go big, and go bright.
You do need to understand that it will have a very small effect on people seeing you while you are riding. Changing the shape of your profile will make you stick out as 'odd' in people's (driver's) perception. Probably less than 1% of drives who woulndn't see you already, would see you as a result. given how many drivers there are.... that's not a bad thing at all. Just don't rely on it.
IMHO, it's way more of a conversation starter than a safety device. Bikes are about personal expression. If you want to look like you stepped out of a Mad Max movie, good for you.