So are you saying a 100 Ohm resistor should be enough that the 220k used in the examples is just to play it safe?
Because I don't have many blue led's I figured to play it safe and use multiple resistors.
I also noticed that it was much much brighter than the green and red leds
LEDs vary a LOT in efficiency. There are "super bright" LEDs that are much brighter with the same milliwatts. The specs will usually show brightness as mcd at the rated current.... Just looking at my Jameco catalog I see LEDs from less than 10 mcd to over 5000 mcd.
Power is (Watts or milliwatts) is calculated Voltage X Current. So a blue LED at 3V and 20mA is consuming 50% more power than a red LED at 2V and 20mA.
If you want to work within optimum parameters then it is essential that you get hold of manufacturers data sheets for the LEDs being used.
are you sure you didn't slip up and power it without the resistor, even for a split second?
The Led's that I have came in an arduino starter kit. They didn't come with data sheets, I guess the makers of the kits figured newbs wouldn't know what to do with a data sheet anyway. Given that I myself am still trying to figure out how to read a datasheet
Click on the name of the component to download the datasheet of the part. This document will describe the design and functionality of the component.
3 LEDs (blue)
this kit ?
and you'll see that there is already an internal resistor, thus it needs to be powered at 12V (not 5V)