Programming a flex sensor to RGB LED's

Other Hardware Sensors
1

I feel like I am almost there, there is just something wrong. The red LED turns off when it goes under 242, but I don't know why the LED won't change to yellow and green.

/*
  Analog input, analog output, serial output
 
 Reads an analog input pin, maps the result to a range from 0 to 255
 and uses the result to set the pulsewidth modulation (PWM) of an output pin.
 Also prints the results to the serial monitor.
 
 The circuit:
 * potentiometer connected to analog pin 0.
   Center pin of the potentiometer goes to the analog pin.
   side pins of the potentiometer go to +5V and ground
 * LED connected from digital pin 9 to ground
 
 created 29 Dec. 2008
 modified 9 Apr 2012
 by Tom Igoe
 
 This example code is in the public domain.
 
 */

// These constants won't change.  They're used to give names
// to the pins used:
const int analogInPin = A0;  // Analog input pin that the flex sensor is attached to
const int analogOutPin = 9; // Analog output pin that the LED is attached to

int sensorValue = 0;        // value read from the flexsensor
int outputValue = 0;        // value output to the PWM (analog out)
int redPin   = 7;   // Red LED,   connected to digital pin 5
int greenPin = 6;  // Green LED, connected to digital pin 6
int bluePin  = 5;  // Blue LED,  connected to digital pin 7

void setup() {
  
  // sets the pins as output
  pinMode(redPin,   OUTPUT);  
  pinMode(greenPin, OUTPUT);   
  pinMode(bluePin,  OUTPUT);
  
  // initialize serial communications at 9600 bps:
  Serial.begin(9600); 
  
}
/*
void outputColor(int red, int green, int blue) {
  
  analogWrite(redPin, red);
  analogWrite(bluePin, blue);
  analogWrite(greenPin, green);    
  
}
*/

void loop() {
  // read the analog in value:
  sensorValue = analogRead(analogInPin);            
  // map it to the range of the analog out:
  outputValue = map(sensorValue, 0, 1023, 0, 255);  
  // change the analog out value:
  analogWrite(analogOutPin, outputValue);           

  // print the results to the serial monitor:
  Serial.print("sensor = " );                       
  Serial.print(sensorValue);      
  Serial.print("\t output = ");      
  Serial.println(outputValue);   

  // wait 2 milliseconds before the next loop
  // for the analog-to-digital converter to settle
  // after the last reading:
  delay(2); 

  flexvalue();

}

void flexvalue() {

  int sensorValue = analogRead(A0);
 
   if (sensorValue > 130 && sensorValue < 240 ){
     
      digitalWrite(bluePin, LOW); 
      digitalWrite(redPin, LOW);
      digitalWrite(greenPin, HIGH);
      
    }
    
    else if (sensorValue > 159 && sensorValue < 241){
      
      digitalWrite(bluePin, LOW); 
      digitalWrite(redPin, HIGH);
      digitalWrite(greenPin, HIGH);
      
    }
    
     else if (sensorValue > 242 && sensorValue < 400){
       
      digitalWrite(bluePin, LOW); 
      digitalWrite(redPin, HIGH);
      digitalWrite(greenPin, LOW);
    
        }
  
}
2

The if ranges were overlapping and unnecessary "complex"

try this as a starter (use CTRL-T to auto align the code)
removed unneeded comments and added some (in capitals to see them easily)

// These constants won't change.  They're used to give names
// to the pins used:
const int analogInPin = A0;  // Analog input pin that the flex sensor is attached to
const int analogOutPin = 9; // Analog output pin that the LED is attached to
const int redPin   = 7; 
const int greenPin = 6;
const int bluePin  = 5;

int sensorValue = 0;        // value read from the flexsensor
int outputValue = 0;        // value output to the PWM (analog out)


void setup() 
{
  pinMode(redPin,   OUTPUT);  
  pinMode(greenPin, OUTPUT);   
  pinMode(bluePin,  OUTPUT);

  Serial.begin(9600); 
}


void loop() 
{
  sensorValue = analogRead(analogInPin);            
  outputValue = map(sensorValue, 0, 1023, 0, 255);  
  analogWrite(analogOutPin, outputValue);           

  Serial.print("sensor = " );                       
  Serial.print(sensorValue);      
  Serial.print("\t output = ");      
  Serial.println(outputValue);   

  // wait 2 milliseconds before the next loop
  // for the analog-to-digital converter to settle
  // after the last reading:
  delay(2); 

  flexvalue();

}

void flexvalue()
{
  // int sensorValue = analogRead(A0); // WAS ALREADY READ !

  if (sensorValue < 200 )
  {
    digitalWrite(bluePin, LOW); 
    digitalWrite(redPin, LOW);
    digitalWrite(greenPin, HIGH);
  }
  else if (sensorValue < 300)
  {
    digitalWrite(bluePin, LOW); 
    digitalWrite(redPin, HIGH);
    digitalWrite(greenPin, HIGH);
  }
  else if (sensorValue < 400)
  {
    digitalWrite(bluePin, LOW); 
    digitalWrite(redPin, HIGH);
    digitalWrite(greenPin, LOW);
  }
  else  // ADDED THIS CASE TO CATCH ALL NON COVERED VALUES IN YOUR CODE
  {
    digitalWrite(bluePin, HIGH); 
    digitalWrite(redPin, HIGH);
    digitalWrite(greenPin, HIGH);
  }

}