again, this is one way of doing it.
put a if statement in your loop that has a boolean(lightEffects) in it. the boolean is changed by the button press code i gave earlier.
boolean lightEffects = true;
boolean twa = true;
long lastTime;
int flashTime = 500;
if(lightEffects)
{
if(lastTime ==0)
{
Serial.println("ON");
lastTime = millis();
}
else if(millis() - lastTime > flashTime)
{
Serial.println("OFF");
if(twa)
{
lastTime = millis()+flashTime;
twa= false;
}
}
else if(millis() - lastTime < flashTime)
{
if(!twa)
{
lastTime = millis();
}
Serial.println("ON");
}
}