Toyota Ambient Light

Looking for any help I can get here. I am looking to replicate the ambient lighting found in my wife’s Mercury Mariner into my car. I want to use an Arduino Pro Mini 328 - 5V/16 MHz. I plan to power both the Arduino and the LED’s with a 5V DC/DC Converter. I only plan on driving 6-8 RGB LED’s (front floor boards, rear floor boards, cupholders and center console). I want to program it to every time i push the switch it changes to one of 8 or so colors and then a last option of doing some kind of transition effect to cycle through. One of the real challenges I am facing lately is the switch for this. I would really like to tie it in to a toyota dash switch to look stock instead of mounting a hidden button somewhere. It was suggested to me to get a momentary switch “normally open” for this. Is this correct? I would think it would be the opposite.Can you put me on the right track for the coding of this. Thanks in advance for any help I can get. I really look forward to starting this project as quick as I can.