Voltage regulation on the high side of a Darlington array?
NOTE - these answers were in the process of being given before Jippie's comments were apparent. His comments I agree with.

1) Resistance = (3.3 -Vled)/0.08 and for a Vled of 2.2v R = (3.3 - 2.2)/0.08 = 13.75 ohms.

You got 18.75 ohms so someone is wrong; either you or me.

2) The darlingtons are an array that "grounds" a load connected to the 3.3V rail so basically no, the LEDs are connected in the "high-side" BUT yes, they can be PWM'd

2a) Darlingtons are probably not the best choice because they "drop" about 0.6V when driving a load and you haven't got all that much to play with looking at the green and blue LED specs you have in your post

2b) Best to use conventional transistor, not those configured as darlingtons

3) the common pin on the DA is grounded, the LEDs via resistors (see (1)) connect to 3V3

4) Don't do that - do (3)

5) digest this advise and decide if (5) is a relevant question

6) possibly not but digest the other answers first

7) you can use a shift register to save on IO and you can use fets