Basic question about LEDs with USB chip

Hi, I'm working on a device that uses a PIC chip to control 6
terminals via USB. The terminals can be signaled on/off independently
using 6 optocouplers. I would also like to add 6 indicator LEDs.

USB is of course 5V and I believe the PIC is sending about 5V out.

I'm now using 470 Ohm resistors before each of the 6 optocouplers, but
it's my understanding that in order to add indicator LEDs in series, I
would put resistors in front of them separately using a total of 12 X
~470/2 LEDs.

So my question is whether there are power issues involved in using
this many LEDs. Since LEDs take 3.3V, does that mean I need to have
3.3*12=40 volts, or does the USB power supply somehow keep up with
what is needed??

.

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