I have never owned an RC car ever. I just bought the vaterra police Camaro. I purchased a siren and led light bar and front bar. I also want to get some headlights, tail lights and flashing blue and red for the front and rear. Something like this. https://youtu.be/YJh_ZzkEtI4. My question is would a 3 channel remote and receiver work? I’m also getting a Servo to be able to alternate lights and sirens off and on and the different modes. I have no idea if it will work. Any suggestions? My remote specs: FLYSKY RC 3 CH Transmitter TX FS-GT3B For CAR Boat 2.4Ghz 2.4g w/ Receiver

a 3 channel will only give you three options to use. A 4 channel will give you 4 . your steering and throttle will take up two options

Why are you trying to use a servo for something it is not designed for? You don't use a servo for turning lights on and off. You use them to move things I.e. a steering link or throttle link on a nitro car.

https://www.amainhobbies.com/vaterra...xoCVTgQAvD_BwE

Guessing your getting something like this. The controller that it comes with will have all the flashing functionality. To turn it off and on you can use something like this.

https://hobbyking.com/en_us/turnigy-...E&gclsrc=aw.ds

Or this

https://www.ebay.com/itm/Two-Way-Cha....c100677.m4598

If your doing something more custom then items like this might down as well.
HobbyPartz Flash LED Light Kit for RC Cars

That's not necessarily true, you can use a donor servo as a controller board to enable light features, I've also used channel mixing for brake lights too:

https://www.youtube.com/watch?v=p_34oSUgtGs

a 4 channel radio would be best ..a few different ways to run lights..a Y splitter on 3rd channel.. no servo really needed..

Learn something new everyday.