Utilizing Array with RGB
First, these statements:

if (buttonState = Buttons[0])


are doing an assignment, not a test for equality. You want:

if (buttonState == Buttons[0])
//               ^Notice


Next, pinMode takes two integers, but you are passing an array. You can use a loop to call pinMode multiple times:

for (int i = 0; i &lt; sizeof(Buttons) / sizeof(Buttons[0]); i++) {
     pinMode(Buttons[i], INPUT);
}


Same goes for digitalRead(). You need to read the state for each button:

buttonState = digitalRead(Buttons[0]);
if (buttonState == HIGH) {
   ....
}
buttonState = digitalRead(Buttons[1]);
if (buttonState == HIGH) {
   ....
}
//etc