There are thousands of ways to take your car, and turn it into something that's a more unique expression of your own personal tastes. It's certainly true that a lot of people aren't happy with simply leaving their car in its stock form, but if the idea of installing strobe lights on your private car or truck, it's important to make sure that it's kosher in the eyes of the law.
Many of the details concerning the legality of aftermarket strobe lights on the highway will vary from state to state. However, there are some common themes regarding this issue that are fairly universal. They are regulations that dictate both the brightness and positioning of strobe lights, as well as the color that they're allowed to be. If your vehicle is discovered to be in violation, heavy fines or other penalties are a likely result.
First and foremost, emergency strobe lights that are either red or blue are, by and large, disallowed. There are some exceptions, but the general spirit of the law is that civilian vehicles should not appear to have the same features as those of law enforcement. This includes LED light bars mounted on the roof of your car, or blue LED modules on your dashboard. These kinds of lights can confuse other drivers as to your identity, and have been used by people in the past to impersonate law enforcement officers. It's a fairly serious offence if you're caught doing it.
Another general rule is that, regardless of color, there is a cap on how bright LED strobe lights can be. Typically, the limit is set at roughly the equivalent of the lighting power of 300 candles, but this is another parameter that can vary somewhat based on your location. The general idea here is that civilians can be allowed to have strobe lights, but that they shouldn't be bright enough to compete with other major lighting components of the vehicle. In other words, you can't have one that's as bright as, say, your brake lights.
There's certainly enough room that people can still legally come up with all kinds of ways to put unique touches on how their car or truck looks to people, including a plethora of options for interior lighting. As long as you keep these limits in mind, you're really only limited by your own imagination.