Typically the forward voltage of an LED is between 1.8 and 3.3 volts. It varies by the colour of the LED typically drops around 1.7 to 2.0 volts, but since both voltage drop and light frequency increases with band gap, the blue LED may drop around 3.0 - 3.3 volts.
Play with the different resistor values, source and LED voltages, to determine optimum brightness and peak current. Running the LED's at less than optimum voltage, greatly extends their operational lifespan.
It's always fun learning! 👍
