I'm building a project where I will be lighting up 2 RGB LEDs using PWM. Since the Netduino only has 4 PWM pins (of which I will only use 3 - one pin each for the R, G, and B values respectively), I need a way to be able send the signal to either LED or both. Something like the following:

What component(s) do I need for that black box? I considered something like a TLC 5940 PWM Driver, but I want to be able to power this off of the Netduino itself (i.e. no external power source). Do I just use a bunch of AND gates?