Trouble trying to turn a stepper while a button is pressed down
You don't set the pin itself:

Change

if (buttonPinBlue == HIGH) {


to

if (digitalRead(buttonPinBlue) == HIGH) {


Also you don't have to set the pin every time, only one time is enough: in function setup should be the following line (and it can be removed from the function stepp:

pinMode(buttonPinBlue, INPUT);


Note that if you want to use a 'click' to move to the next item, you have to debounce the button; on the Arduino site check for button debouncing: https://www.arduino.cc/en/Tutorial/Debounce