kustom:
Yeah I do have lots of them, but considering that I should finish the project within a next few weeks, I'll go with safer route and put 220 Ohm resistors.
In my experience of buying cheap leds from eBay, I would test them for as long as time allows, regardless of the resistor value!
PS. How many Arduino outputs are you using to run the matrix, 7? Did you realise it can be done with 4?