Thank you all for replying.
@Boffin1
So this is how it works. The voltage drop (Vd) across the resistor is first calculated.
It is 2V (since 5v-3v). Now we decide on the value of resistor so that we get desired current.
Aha! I had tried to read through various posts, but was confused & had to post this noobish question.
(I remember the current/voltage bifurcation always used to confuse me 
)
Thanks all. This was an education. 
Boffin1:
Do you want to use 2 LEDs as they are in different locations, or was it to try and get more illumination ?
For more illumination. Actually, I want to connect at least 2 RGB LEDs to 3 PWM Arduino pins.
Are there some tutorials to brush up the electronics basics (with respect to Arduino.)?
Thanks again.