Actually in most cases the final mission #7 of the colony chain gives you a blue because you have I believe a 80% change of success and 20% chance of crit - it's a 15 min assignment and if you crit on that one you also get a purple.
But he is claiming that he is the avg doffer and somehow by his own math needs 25 purples a week? - I find his motives highly suspect and so would anyone who is a true doffer such as myself.
Colony Mission 7/7 always gives a Blue. Never a Purple. 100% chance of a Blue. Crit means absolutely nothing. Failure means absolutely nothing. And you can only do it once, so being 15 minutes is not of any importance. As a "true doffer such as yourself", you should have known that.
If you're feeding a Starbase and sending those Purple DOFFs to several characters, 25/week isn't as much as you seem to think.
Besides, you claim to have 1500 Purple DOFFs. The DOFF system first appeared on December 1st, 2011. That was 47 weeks ago. Guess how many you've acquired per week. 31.9 purple DOFFs / week. Should I find your motives highly suspect ?