Arduino　カウンターがなぜか進みません。

Arduino初心者です。
3色LEDを1色づつ順番に光らせようとしているのですが、colorSwitchが1から進まず、出来ません。
試しにif(colorSwitch = 0){...}else if(colorSwitch = 1){...}else if(colorSwitch = 2){...}を削除してみると、なぜかcolorSwitchのカウンターは回りました。何が間違ってるのかさっぱりです、、、分かる方おられましたらご教授ください。

Arduino
1int red = 9;
2int blue = 10;
3int green = 11;
4int brightnessRed = 0;
5int brightnessGreen = 0;
6int brightnessBlue = 0;
7int fadeAmount = 5;
8int loopCount = 0;
9int colorSwitch = 0;
10
11void setup() {
12  // put your setup code here, to run once:
13  pinMode(red, OUTPUT);
14  pinMode(green, OUTPUT);
15  pinMode(blue, OUTPUT);
16  Serial.begin(9600);
17  
18}
19
20void loop() {
21  // put your main code here, to run repeatedly:
22  analogWrite(red, brightnessRed);
23  analogWrite(green, brightnessGreen);
24  analogWrite(blue, brightnessBlue);                                
25
26  loopCount++;
27
28  if(loopCount >= 103){//Fadeで光って消えるまでのループ回数が102回
29    loopCount = 0;
30    colorSwitch++;
31    }
32
33    if(colorSwitch >= 3){
34      colorSwitch = 0;
35    }
36
37
38
39    if(colorSwitch = 0){
40        brightnessRed = brightnessRed + fadeAmount;
41
42        if(brightnessRed == 0 || brightnessRed == 255){
43            fadeAmount = -fadeAmount;
44        }
45        delay(30);
46        
47  }else if(colorSwitch = 1){
48        brightnessGreen = brightnessGreen + fadeAmount;
49
50        if(brightnessGreen == 0 || brightnessGreen == 255){
51            fadeAmount = -fadeAmount;
52        }
53        delay(30);
54        
55  }else if(colorSwitch = 2){
56        brightnessBlue = brightnessBlue + fadeAmount;
57
58        if(brightnessBlue == 0 || brightnessBlue == 255){
59            fadeAmount = -fadeAmount;
60        }
61        delay(30);
62  }
63
64    
65    Serial.print("colorSwitch:");
66    Serial.print(colorSwitch);
67    Serial.print("loopCount:");
68    Serial.println(loopCount);
69}
70