Hi, thanks for the replies. ok, I was talking rubbish when I said they are 5v, having looked at them I have no idea what they are, I think their just old ones I have from somewhere, probably ebay.
I've got a project box with an LCD display that I'm using for a climate control and I want the leds to indicate extremes, ie temp over defined requirement or co2 level exceeded.
So, I'm going to have a few leds attached to pins, I'm guessing each will need a resistor, I was thinking I'd use an external power supply, I have a 9v psu powering my Arduino with a step down board (9v-5v) powering my LCD and some sensors so I thought I'd take a feed from that to power the leds save taking power from the Arduno.
What do you reckon, should I just buy a bunch of transistors to switch on my leds or is there a chip containing multiple transistors available, or maybe I don't even need transistors and I can just power them straight from the pins, using resistors of course 