Please help me

Projects General Guidance
6

I suggest you add another variable byte selectedColour =0; which can take any of the values 0, 1, 2 for Red Green or Blue.
Also make 3 variables to hold the value for each colour byte blueVal = 0; etc.

Then read check when your button changes from OFF to ON with something like

buttonVal = digitalRead(buttonPin);
if (buttonVal == LOW && prevButtonVal == HIGH) {
   selectedColour += 1; // move to next colour
   if (selectedColour > 2) {
      selectedColour = 0;
   }
}
prevButtonVal = buttonVal;

(That could all go in a buttonRead() function)

Then, elsewhere in your program you have something like

if (selectedColour == 0) {
   redVal = analogVal / 4;
}
else if (selectedColor == 1) {
   blueVal = analogVal / 4;
}
else {
   greenVal = analogVal / 4;
}

And if you were to use an array to hold the colour values it could be even shorter

colourVal[selectedColour] = analogVal / 4;

The trick is to separate the reading of the button from the setting of the colours by using a variable as an intermediary. The variable will remember its setting until the next time it is changed.

...R