 led fade with pir and sound sensor

Hello! so i just finished my first project and im here to get some final help

The idea
the idea is to have a rgb led sensor connected to a nano, a pir motion sensor detects movement and turns it on, when no motion it turns off, clapping makes it change color

the problem
the problem i have is that i want it to fade up when motion is seeen and fade down (with current color ) when no motion, so i need some kind of alpha value but i dont know how to do it #define REDPIN 9
#define GREENPIN 10
#define BLUEPIN 11
int sensor = 2;             //motion sensor
int state = LOW;             // by default, no motion detected
#define FADESPEED 10     // make this higher to slow down
int r =100;
int g =100;
int b =100;
int x;
int a=1;
int z=1;
int button=6;
int val=0;
void setup() {
pinMode(sensor, INPUT);
pinMode(button,INPUT);
Serial.begin(9600);
pinMode(REDPIN, OUTPUT);
pinMode(GREENPIN, OUTPUT);
pinMode(BLUEPIN, OUTPUT);

}

void loop() {

if (digitalVlaue) { // if clap
r=random(255);
g=random(255);
b=random(255);

}

if (sensorValue) { // if motion seen

analogWrite(BLUEPIN,b);
analogWrite(GREENPIN,g);
analogWrite(REDPIN,r);
a=1;
}

if(!sensorValue){   // if motion not seen

for (x = 255; x >= 0; x--) {
analogWrite(BLUEPIN,x);
analogWrite(GREENPIN,x);
analogWrite(REDPIN,x);

a=0;
z=1;
} }

}}

any ideas? /// Kaffex

solved void loop() {

analogWrite(BLUEPIN,b*a);
analogWrite(GREENPIN,r*a);
analogWrite(REDPIN,g*a);

if (digitalVlaue) { // if clap
r=random(25);
g=random(25);
b=random(25);
}

if (sensorValue) { // if motion seen

while(a<10){
a++;
//Serial.println(a);
analogWrite(BLUEPIN,b*a);
analogWrite(GREENPIN,r*a);
analogWrite(REDPIN,g*a);
}

}

if(!sensorValue){   // if motion not seen
while(a>0){
a--;
analogWrite(BLUEPIN,b*a);
analogWrite(GREENPIN,r*a);
analogWrite(REDPIN,g*a);
//Serial.println(a);