I actually thought about that when coloring him, because I think in the episode he turns a weird yellow or something when he tries smoking. My main concern was trying to get a good skin color for him, though, so I tried at that instead.
Nicely done...love your Amy. You brought up a good point about Kif...it's easy to get him too dark or too light. I use Prismacolor Spearmint, which is also what I use on the PE ship - that might be too dark, though...[link]
That's not too bad a color for him. It's kind of close to the green I used behind Zoidberg in this set. I have Dick Blick markers, and that one is 'sage.' Once I finished the card, I immediately thought I should have used it. It's the same issue with Zapp's dress uniform; in reality, it's supposed to be a very, VERY light pale green. I guess it's just part of the deal with markers.
I got so lucky with Zapp's duty uniform - Copic garnett works so well. I recently did a tutorial [link] , I went about half nuts trying to decided what to do with Leela's hair. BTW, I really like the idea of those sketch cards.