And... if brightness equality is important, it is probably easiest if you using one of those 25 turn trim pots to help with determining the resistance.
I used to do it mathematically to give different color led the same current. But, same current != same brightness.
Now I use a trimpot to get them to appear equally bright, then use a DMM to find out what resistance it is. Then I do some quick calculation to make sure that is within the LED's spec. If all is well, I find a fix resistor closest to the measured value and then solder it in.