Arduino Code Not Processing Serial Output - c

Question

I am using a Arduino Uno for an embedded systems course. My assignment is that I have to write a function that implements these specifications. Take an input from the user (‘R’, ‘G’, ‘B’) and display Red, Green or Blue. The function name must be dispColor(), the input must be char a and their is no return. My code is below, however whenever I type in an input I receive no output. Where is the error in my code?
String dispColor(char){
char a = Serial.read();
if (a == "R")
Serial.print("Red");
else if (a == "G")
Serial.print("Green");
else if (a == "B")
Serial.print("Blue");
}
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
String dispColor();
}
void loop() {
// put your main code here, to run repeatedly:
}
My Updated code
void dispColor(char a){
if(Serial.available()){
a = Serial.read();
if(a == 'R')
Serial.print("Red");
else if(a == 'G')
Serial.print("Green");
else if(a == 'B')
Serial.print("Blue");
}
}
void setup() {
Serial.begin(9600);
Serial.println("Please type in R, G, or B.");
dispColor();
}
void loop() {
}

Answer 1

As says the comment in setup ("// put your setup code here, to run once:", that code will be executed only once, so when you're ready to "type an input", there will not be any code running to read it.
Thus, one thing you'll definitely need to do is move dispColor to loop.
There are a few more mistakes:
You're comparing a char with a String
You should be passing a parameter to dispColor, not reading from within it
You should probably only be calling dispColor if there's input available.
Have a look at https://www.arduino.cc/reference/en/language/functions/communication/serial/read/ to get started!

Answer 2

I figured it out!
My new code
void setup()
{
Serial.begin(9600);
Serial.println("Please type in R, G, or B.");
}
void dispColor(char a)
{
while(!Serial.available());
a = Serial.read();
if(a == 'R')
Serial.println("Red");
else if(a == 'G')
Serial.println("Green");
else if(a == 'B')
Serial.println("Blue");
Serial.print('\n');
}
void loop() {
char a;
dispColor(a);
}